Self-adhesive dental composite resin

ABSTRACT

The present invention provides a self-adhesive dental composite resin maintaining mechanical strength, showing excellent storage stability, undergoing little change in transparency and properties of the paste during long-term storage, and having a small solidification risk during long-term storage. The present invention relates to a self-adhesive dental composite resin comprising: an acid group-containing (meth)acrylic polymerizable monomer (a); a polyfunctional (meth)acrylic polymerizable monomer (b) containing no acid group; a photopolymerization initiator (c); and a filler (d), wherein the filler (d) is treated with a surface treatment agent and has an average particle diameter of 0.01 to 50.0 μm, the surface treatment agent comprises a silane coupling agent (A) represented by the following general formula (1): 
       CH 2 ═C(R 1 )—COO—(CH 2 ) p —Si—R 2   q R 3   (3-q)   (1), and
 
     an organosilazane (B) represented by the following general formula (2): 
       R 4 R 5 R 6 —Si—NH—Si—R 7 R 8 R 9   (2).

TECHNICAL FIELD

The present invention relates to a self-adhesive dental composite resin. More specifically, the present invention relates to a self-adhesive dental composite resin having sufficient mechanical strength, having excellent storage stability, undergoing little change in transparency and properties of the paste during long-term storage, and having a small solidification risk in a long-term perspective.

BACKGROUND ART

Conventionally, in restorative treatment of dental caries and broken or chipped teeth caused by dental caries, dental adhesives and dental composite resins are generally used. Such restorative treatment is carried out according to the following procedure. First, caries is excavated to form a cavity, a dental adhesive is applied to the cavity, and then the adhesive thus applied is irradiated with visible light so as to cure the adhesive. Next, a dental composite resin is placed on the cured adhesive layer, and finally, the dental composite resin thus placed is irradiated with visible light so as to cure the resin.

In the above-described restoration method, two materials, i.e., a dental adhesive and dental composite resin, are used. Recently, self-adhesive dental composite resins having self-adhesive properties have been developed and practically used as materials usable for restorative treatment with fewer steps and without the use of a dental adhesive.

Such a self-adhesive dental composite resin contains an acid group-containing polymerizable monomer having been used in a dental adhesive material as a component to impart adhesion to tooth structures, in addition to conventional dental composite resin components, such as a polyfunctional polymerizable monomer and a filler for providing mechanical strength and a polymerization initiator for improving curability (for example, Patent Literatures 1 and 2).

(Meth)acrylates are generally used as polymerizable monomers contained in dental composite resins. For example, in Patent Literatures 1 and 2, a polymerizable monomer having an acid group such as a phosphate or carboxy group is contained to impart self-adhesion and improve the bond strength to tooth structures.

A component (for example, oxides, carbonates, and hydroxides of alkaline-earth metals, such as calcium, magnesium, and strontium, and acid-reactive fluoroaluminosilicate glass) commonly used in dental composite resins is known to be disadvantageous as a filler contained in self-adhesive dental composite resins, because in self-adhesive dental composite resins, such a filler causes an acid-base reaction, neutralization, salt formation, or a chelation reaction with a polymerizable monomer having an acid group to impair the self-adhesiveness itself. Therefore, to overcome this disadvantage, it has been proposed to select a filler, such as a silica filler treated with a silane coupling agent, poorly reactive with an acid component as a filler contained in self-adhesive dental composite resins (Patent Literature 2).

CITATION LIST Patent Literature

Patent Literature 1: JP 2008-260752 A

Patent Literature 2: JP 2015-507610 A

SUMMARY OF INVENTION Technical Problem

When, for example, the silica filler described in Patent Literature 2 and being unreactive with an acid component is used, a reaction between the filler and acid component is suppressed; however, while stored, the resultant self-adhesive dental composite resin may undergo a large change in transparency and properties of the paste or may be solidified.

It is therefore an object of the present invention to provide a self-adhesive dental composite resin maintaining mechanical strength by containing a polyfunctional polymerizable monomer, filler, and polymerization initiator as is the case for conventional dental composite resins, showing excellent storage stability, undergoing little change in transparency and properties of the paste during long-term storage, and having a small solidification risk during long-term storage.

Solution to Problem

That is, the present disclosure provides the following inventions.

[1] A self-adhesive dental composite resin, comprising:

an acid group-containing (meth)acrylic polymerizable monomer (a);

a polyfunctional (meth)acrylic polymerizable monomer (b) containing no acid group;

a photopolymerization initiator (c); and

a filler (d), wherein

the filler (d) is treated with a surface treatment agent and has an average particle diameter of 0.01 to 50.0 μm,

the surface treatment agent comprises a silane coupling agent (A) represented by the following general formula (1):

CH₂═C(R¹)—COO—(CH₂)_(p)—Si—R² _(q)R³ _((3-q))  (1),

wherein R¹ is a hydrogen atom or a methyl group, R² is an optionally substituted hydrolyzable group, R³ is an optionally substituted C₁ to C₃ alkyl group, p is an integer of 1 to 13, and q is 2 or 3, and an organosilazane (B) represented by the following general formula (2):

R⁴R⁵R⁶—Si—NH—Si—R⁷R⁸R⁹  (2),

wherein R⁴, R⁵, and R⁶ are each independently a hydrogen atom or an optionally substituted C₁ to C₃ alkyl group, at least one of R⁴, R⁵, and R⁶ is an optionally substituted C₁ to C₃ alkyl group, R⁷, R⁸, and R⁹ are each independently a hydrogen atom or an optionally substituted C₁ to C₃ alkyl group, and at least one of R⁷, R⁸, and R⁹ is an optionally substituted C₁ to C₃ alkyl group.

[2] The self-adhesive dental composite resin according to [1], wherein R² is an unsubstituted hydrolyzable group, R³ is an unsubstituted C₁ to C₃ alkyl group, R⁴, R⁵, and R⁶ are each independently a hydrogen atom or an unsubstituted C₁ to C₃ alkyl group, at least one of R⁴, R⁵, and R⁶ is an unsubstituted C₁ to C₃ alkyl group, R⁷, R⁸, and R⁹ are each independently a hydrogen atom or an unsubstituted C₁ to C₃ alkyl group, and at least one of R⁷, R⁸, and R⁹ is an unsubstituted C₁ to C₃ alkyl group. [3] The self-adhesive dental composite resin according to [1] or [2], wherein R² is an unsubstituted linear or branched C₁ to C₆ alkoxy group. [4] The self-adhesive dental composite resin according to any one of [1] to [3], wherein R¹ is a methyl group. [5] The self-adhesive dental composite resin according to any one of [1] to [4], wherein p is 2 to 10. [6] The self-adhesive dental composite resin according to any one of [1] to [5], wherein q is 3. [7] The self-adhesive dental composite resin according to any one of [1] to [6], wherein the silane coupling agent (A) is at least one selected from the group consisting of 2-methacryloyloxyethyltrimethoxysilane, 3-methacryloyloxypropyltrimethoxysilane, 4-methacryloyloxybutyltrimethoxysilane, 5-methacryloyloxypentyltrimethoxysilane, and 6-methacryloyloxyhexyltrimethoxysilane. [8] The self-adhesive dental composite resin according to any one of [1] to [7], wherein the organosilazane (B) is at least one selected from the group consisting of 1,1,3,3-tetramethyldisilazane, 1,1,1,3,3,3-hexamethyldisilazane, and 1,1,1,3,3-pentamethyldisilazane. [9] The self-adhesive dental composite resin according to any one of [1] to [8], wherein the molar ratio between the silane coupling agent (A) and the organosilazane (B) is [silane coupling agent (A)]:[organosilazane (B)]=1:1 to 1:20. [10] The self-adhesive dental composite resin according to any one of [1] to [9], wherein

the content of the acid group-containing (meth)acrylic polymerizable monomer (a) is 1 to 40 parts by mass and the content of the polyfunctional (meth)acrylic polymerizable monomer (b) containing no acid group is 30 to 95 parts by mass in 100 parts by mass of the total polymerizable monomer components, and

the content of the photopolymerization initiator (c) is 0.001 to 20 parts by mass and the content of the filler (d) is 1 to 80 parts by mass with respect to 100 parts by mass of the total polymerizable monomer components.

[11] The self-adhesive dental composite resin according to any one of [1] to [10], further comprising an amide proton-containing polyfunctional (meth)acrylamide polymerizable monomer (e). [12] The self-adhesive dental composite resin according to [11], wherein the content of the amide proton-containing polyfunctional (meth)acrylamide polymerizable monomer (e) is 0.5 to 30 parts by mass in 100 parts by mass of the total polymerizable monomer components. [13] The self-adhesive dental composite resin according to any one of [1] to [12], further comprising a hydrophilic monofunctional polymerizable monomer (f). [14] The self-adhesive dental composite resin according to [13], wherein the hydrophilic monofunctional polymerizable monomer (f) is at least one selected from the group consisting of a hydrophilic monofunctional (meth)acrylate polymerizable monomer and a hydrophilic monofunctional (meth)acrylamide polymerizable monomer. [15] The self-adhesive dental composite resin according to [13] or [14], wherein the content of the hydrophilic monofunctional polymerizable monomer (f) is 1 to 30 parts by mass in 100 parts by mass of the total polymerizable monomer components. [16] The self-adhesive dental composite resin according to any one of [1] to [15], being a one-part self-adhesive dental composite resin.

Advantageous Effects of Invention

The present invention provides a self-adhesive dental composite resin having sufficient mechanical strength, showing excellent storage stability, undergoing little change in transparency and properties of the paste during long-term storage, and having a small solidification risk during long-term storage. Additionally, the self-adhesive dental composite resin of the present invention has excellent adhesiveness to tooth structures.

BRIEF DESCRIPTION OF DRAWING

FIG. 1 illustrates a reaction mechanism in which an organosilazane (B) according to an embodiment of the present invention is 1,1,1,3,3,3-hexamethyldisilazane.

DESCRIPTION OF EMBODIMENTS

The self-adhesive dental composite resin of the present invention comprises: an acid group-containing (meth)acrylic polymerizable monomer (a);

a polyfunctional (meth)acrylic polymerizable monomer (b) containing no acid group;

a photopolymerization initiator (c); and

a filler (d), wherein

the filler (d) is treated with a surface treatment agent and has an average particle diameter of 0.01 to 50.0 μm,

the surface treatment agent comprises a silane coupling agent (A) represented by the following general formula (1):

CH₂═C(R¹)—COO—(CH₂)_(p)—Si-R² _(q)R³ _((3-q))  (1),

wherein R¹ is a hydrogen atom or a methyl group, R² is an optionally substituted hydrolyzable group, R³ is an optionally substituted C₁ to C₃ alkyl group, p is an integer of 1 to 13, and q is 2 or 3, and an organosilazane (B) represented by the following general formula (2):

R⁴R⁵R⁶—Si—NH—Si—R⁷R⁸R⁹  (2),

wherein R⁴, R⁵, and R⁶ are each independently a hydrogen atom or an optionally substituted C₁ to C₃ alkyl group, at least one of R⁴, R⁵, and R⁶ is an optionally substituted C₁ to C₃ alkyl group, R⁷, R⁸, and R⁹ are each independently a hydrogen atom or an optionally substituted C₁ to C₃ alkyl group, and at least one of R⁷, R⁸, and R⁹ is an optionally substituted C₁ to C₃ alkyl group.

In the present specification, the upper limits and lower limits of value ranges (ranges of, for example, the contents of components, values calculated for components, values of physical properties, and values of symbols in formulae) can be combined appropriately.

It is not known exactly why the self-adhesive dental composite resin of the present invention has sufficient mechanical strength, has excellent storage stability, undergoes little change in transparency and properties of the paste during long-term storage, and has no solidification risk during long-term storage. The reasons are probably as follows. That is, the filler (d) has on its surface a functional group represented by —(CH₂)_(p)—OOC—C(R¹)═CH₂ (R¹ is a hydrogen atom or methyl group, and p is an integer of 1 to 13) and derived from a surface treatment with the silane coupling agent (A) and a C₁ to C₃ alkyl group derived from a surface treatment with the organosilazane (B). C₁ to C₃ alkyl groups are repulsive to each other due to their hydrophobicity. Accordingly, even after long-term storage in the form of the self-adhesive dental composite resin, the filler (d) is less likely to aggregate owing to the repulsion between the C₁ to C₃ alkyl groups and high transparency of the paste can be maintained. It is thought that having —(CH₂)_(p)—OOC—C(R¹)═CH₂ on the surface, the filler (d) can be polymerized with a polymerizable group of a polymerizable monomer in the self-adhesive dental composite resin. That makes it possible to further reinforce a bond at the interface between the filler (d) and polymerizable monomer and impart sufficient mechanical strength. —(CH₂)X—OOC—C(R¹)═CH₂ is imparted by a dehydration polycondensation reaction between silanol groups using the silane coupling agent (A) having a polymerizable group, and the C₁ to C₃ alkyl group is imparted by a deammoniation reaction involving the organosilazane (B). In a common treatment known as a conventional technique and using a silane coupling agent (A) alone, a silanol group (—SiOH) yielded by hydrolysis of an alkoxy group of the silane coupling agent (A) and a silanol group (—SiOH) on the surface of a filler (d) are chemically bonded by dehydration polycondensation. This allows the silanol group (—SiOH) on the surface of the filler (d) or silanol group (—SiOH) derived from the silane coupling agent (A) to remain as an unreacted product (hereinafter, such a remaining silanol group will be referred to as “remaining silanol group”). In the present invention, as shown in FIG. 1, the deammoniation reaction between the remaining silanol group (—SiOH) on the surface of the filler (d) or remaining silanol group (—SiOH) derived from the silane coupling agent (A) and the organosilazane (B) can make the remaining silanol group (—SiOH) hydrophobic. It can be thought that this treatment (deammoniation reaction) with the organosilazane (B) can reduce the remaining silanol group (—SiOH) on the surface of the filler (d) or remaining silanol group (—SiOH) derived from the silane coupling agent (A) to a minimum. Therefore, it is less likely that in one paste, a proton (H⁺) yielded from the acid group-containing (meth)acrylic polymerizable monomer (a) which is an essential component for imparting adhesion to the self-adhesive dental composite resin, a hydroxy group (—OH) contained in another polymerizable monomer, or the like causes a strong interaction with the silanol group (—SiOH) due to hydrogen bonding. This is presumably the reason why the properties of the paste are stable during long-term storage and the solidification risk is very low.

Presumably for the above reasons, the self-adhesive dental composite resin comprising the filler (d) has sufficient mechanical strength, undergoes little change in transparency and properties of the paste during long-term storage, and has a small solidification risk during long-term storage.

First, the filler (d) used in the present invention will be described.

The filler (d) has —(CH₂)_(p)—OOC—C(R¹)═CH₂ and the C₁ to C₃ alkyl group on its surface. C₁ to C₃ alkyl groups are repulsive to each other due to their hydrophobicity. Therefore, the filler (d) of the present invention is less likely to aggregate in the self-adhesive dental composite resin owing to the repulsion between the C₁ to C₃ alkyl groups, and is also less likely to aggregate when in powder form.

As the filler (d), any known filler used in dental composite resins can be used without any limitation as long as the filler (d) is treated with a surface treatment agent and has an average particle diameter of 0.01 to 50.0 μm, the surface treatment agent comprises the silane coupling agent (A) represented by the formula (1) and the organosilazane (B) represented by the formula (2). Examples of the filler (d) include: various types of glasses [containing silica as a main component and optionally containing oxides of heavy metals, boron, aluminum, etc., for example: glass powders having typical compositions, such as fused silica, quartz, soda lime silica glass, E-glass, C-glass, borosilicate glass (Pyrex (registered trademark) glass); and glass powders for dental use, such as barium glass (GM 27884 and 8235 manufactured by Schott, and E-2000 and E-3000 manufactured by Esstech, Inc.), strontium borosilicate glass (E-4000 manufactured by Esstech, Inc.), lanthanum glass ceramics (GM 31684 manufactured by Schott), and fluoroaluminosilicate glass (GM 35429, G018-091, and G018-117 manufactured by Schott)]; various types of ceramics; composite oxides such as silica-titania and silica-zirconia; diatomaceous earth; kaolin; clay minerals (such as montmorillonite); activated white clay; synthetic zeolite; mica; calcium fluoride; ytterbium fluoride; yttrium fluoride; calcium fluoride having the surface coated with silica and having a core-shell structure; ytterbium fluoride having the surface coated with silica and having a core-shell structure; yttrium fluoride having the surface coated with silica and having a core-shell structure; calcium phosphate; barium sulfate; zirconium dioxide; titanium dioxide; hydroxyapatite; calcium phosphate having the surface coated with silica and having a core-shell structure; barium sulfate having the surface coated with silica and having a core-shell structure; zirconium dioxide having the surface coated with silica and having a core-shell structure; titanium dioxide having the surface coated with silica and having a core-shell structure; and hydroxyapatite having the surface coated with silica and having a core-shell structure. Among these, the various types of glasses, composite oxides such as silica-titania and silica-zirconia, calcium fluoride having the surface coated with silica and having a core-shell structure, ytterbium fluoride having the surface coated with silica and having a core-shell structure, yttrium fluoride having the surface coated with silica and having a core-shell structure, calcium phosphate having the surface coated with silica and having a core-shell structure, barium sulfate having the surface coated with silica and having a core-shell structure, zirconium dioxide having the surface coated with silica and having a core-shell structure, titanium dioxide having the surface coated with silica and having a core-shell structure, hydroxyapatite having the surface coated with silica and having a core-shell structure, ytterbium fluoride having the surface coated with silica and having a core-shell structure, and yttrium fluoride having the surface coated with silica and having a core-shell structure are suitable because, in that case, the filler (d) can be efficiently reacted with the silane coupling agent (A) or organosilazane (B). One of these may be used alone, or two or more thereof may be used in combination.

The average particle diameter of the filler (d) is 0.01 to 50.0 μm, preferably 0.03 to 20.0 μm, and more preferably 0.05 to 10.0 μm. When the average particle diameter of the filler (d) is within these ranges, sufficient mechanical strength can be obtained, and the paste does not become sticky and thus has good handling properties. In addition, the resultant cured product has high surface smoothness and gloss after polishing or good retention of the smoothness and gloss. In the present specification, the average particle diameter of the filler means the average particle diameter (average primary particle diameter) of the primary particles of the filler.

The average particle diameter of the filler (d) can be determined by particle size distribution analysis or electron microscopic observation. When the average particle diameter is 1.0 μm or more, a particle size distribution analyzer is preferably employed. When the average particle diameter is less than 1.0 μm, electron microscopic observation is preferably employed. To be more specific about the particle size distribution analysis, for example, the average particle diameter can be measured using a 0.2% aqueous solution of sodium hexametaphosphate as a dispersion medium by means of a laser diffraction particle size distribution analyzer (SALD-2100 manufactured by Shimadzu Corporation). To be more specific about the electron microscope observation, for example, the average particle diameter can be determined by taking a photograph of particles by means of a scanning electron microscope (S-4000 manufactured by Hitachi, Ltd.) and measuring the particle diameters of (200 or more) particles observed in a unit area of field of view in the photograph by the use of an image-analyzing particle size distribution analysis software (Macview (Mountech Co., Ltd.)). In this case, the particle diameter of each particle is determined as an arithmetic mean of the maximum and minimum lengths of the particle, and, from the thus determined particle diameters and the number of the particles, the average primary particle diameter is calculated.

The filler (d) used in the present invention is less likely to aggregate and thus can be easily washed with water. Therefore, the use of the filler (d) of the present invention can reduce the contents of ionic impurities, such as an alkali metal, undergoing an acid-base reaction or chelation reaction with the acid group-containing (meth)acrylic polymerizable monomer (a).

The filler (d) can be obtained by surface-treating the materials of the filler (d) with the silane coupling agent (A) represented by the formula (1) and organosilazane (B) represented by the formula (2).

The surface treatment with the silane coupling agent (A) represented by the formula (1) substitutes the functional group derived from the silane coupling agent (A) for a hydroxy group existing on the surface of the filler (d).

The order of the surface treatment of the filler (d) is not particularly limited. For example, the silane coupling agent (A) represented by the formula (1) and organosilazane (B) represented by the formula (2) may be added sequentially or simultaneously to the filler (d) to surface-treat the filler (d) therewith. For example, the filler (d) may be reacted with the silane coupling agent (A) represented by the formula (1) first, subsequently with the organosilazane (B) represented by the formula (2). Alternatively, the filler (d) may be reacted with the organosilazane (B) represented by the formula (2) first, subsequently with the silane coupling agent (A) represented by the formula (1), and then with organosilazane (B) represented by the formula (2).

The method for surface-treating the filler (d) is not particularly limited as long as the method is a method for bonding the silane coupling agent (A) represented by the formula (1) to the surface of the filler (d) by a dehydration polycondensation reaction and a method for bonding the organosilazane (B) represented by the formula (2) to the surface of the filler (d) by a deammoniation reaction. Examples of the method for surface-treating the filler (d) include: a method in which the filler (d) is sprayed under stirring in a mixing chamber with solutions of the surface treatment agents each diluted with a solvent and dried by heating under continuous stirring in the chamber for a certain period of time; and a method in which the filler (d) and surface treatment agents are stirred and mixed in a solvent, followed by heat drying. Examples of the solvent include, but are not particularly limited to, alcohol solvents such as methanol, ethanol, and isopropanol, water, and a mixed solvent thereof. The heating temperature is not particularly limited, and may be around 30 to 90° C.

In the formula (1), R¹ is a hydrogen atom or methyl group. R² is an optionally substituted hydrolyzable group. R³ is an optionally substituted C₁ to C₃ alkyl group. p is an integer of 1 to 13, preferably 2 to 10, more preferably 2 to 8, and even more preferably 2 to 6. q is 2 or 3, and preferably 3.

The optionally substituted hydrolyzable group represented by R² is not particularly limited. Examples of the hydrolyzable group include: linear or branched C₁ to C₆ alkoxy groups such as methoxy, ethoxy, n-propoxy, isopropoxy, n-butoxy, sec-butoxy, isobutoxy, tert-butoxy, pentyloxy, isopentyloxy, hexyloxy, and isohexyloxy groups; a chlorine atom; and isocyanate group. In view of hydrolyzability, the alkoxy group serving as the hydrolyzable group is more preferably a linear C₁ to C₄ alkoxy group selected from methoxy, ethoxy, n-propoxy, and n-butoxy groups, and even more preferably a linear C₁ to C₃ alkoxy group. The hydrolyzable group represented by R² may be unsubstituted. It is preferable as the silane coupling agent (A) that in the formula (1), R¹ be a methyl group, R² be an unsubstituted C₁ to C₆ linear or branched alkoxy group, R³ be an unsubstituted C₁ to C₃ alkyl group, p be 2 to 10, and q be 2 or 3. It is more preferable that in the formula (1), R¹ be a methyl group, R² be an unsubstituted linear or branched C₁ to C₄ alkoxy group, p be 2 to 8, and q be 3. It is even more preferable that in the formula (1), R¹ be a methyl group, R² be an unsubstituted linear or branched C₁ to C₃ alkoxy group, p be 2 to 6, and q be 3.

Examples of the optionally substituted C₁ to C₃ alkyl group represented by R³, R⁴, R⁵, R⁶, R⁷, R⁸, and R⁹ include methyl, ethyl, n-propyl, and isopropyl groups. The alkyl group represented by R³, R⁴, R⁵, R⁶, R⁷, R⁸, and R⁹ may be each individually unsubstituted. As the alkyl group represented by R⁴, R⁵, R⁶, R⁷, R⁸, and R⁹, methyl and ethyl groups are preferred, and a methyl group is more preferred. At least one of R⁴, R⁵, and R⁶ is an optionally substituted C₁ to C₃ alkyl group, two of them may be an optionally substituted C₁ to C₃ alkyl group, all three of them may be an optionally substituted C₁ to C₃ alkyl group. At least one of R⁷, R⁸, and R⁹ is an optionally substituted C₁ to C₃ alkyl group, two of them may be an optionally substituted C₁ to C₃ alkyl group, all three of them may be an optionally substituted C₁ to C₃ alkyl group.

Examples of a substituent in the hydrolyzable group represented by R² and a substituent in the alkyl group represented by R³, R⁴, R⁵, R⁶, R⁷, R⁸, and R⁹ include a halogen atom (fluorine, chlorine, bromine, or iodine atom), carboxy group, hydroxy group, amino group, amino group mono- or di-substituted by a C₁ to C₆ alkyl group, acyl group, and C₁ to C₆ alkyl group. The number of the substituents is not particularly limited. The number of the substituents in the hydrolyzable group represented by R² is 1 to 5. The number of the substituents in the alkyl group represented by R³, R⁴, R⁵, R⁶, R⁷, R⁸ and R⁹ is 1, 2, or 3.

Specific examples of the silane coupling agent (A) represented by the formula (1) include: (meth)acryloyloxymethyltrimethoxysilane, 2-(meth)acryloyloxyethyltrimethoxysilane, 3-(meth)acryloyloxypropyltrimethoxysilane, 4-(meth)acryloyloxybutyltrimethoxysilane, 5-(meth)acryloyloxypentyltrimethoxysilane, 6-(meth)acryloyloxyhexyltrimethoxysilane, 7-(meth)acryloyloxyheptyltrimethoxysilane, 8-(meth)acryloyloxyoctyltrimethoxysilane, 9-(meth)acryloyloxynonyltrimethoxysilane, 10-(meth)acryloyloxydecyltrimethoxysilane, 11-(meth)acryloyloxyundecyltrimethoxysilane, 11-(meth)acryloyloxyundecyldichloromethylsilane, 11-(meth)acryloyloxyundecyltrichlorosilane, 11-(meth)acryloyloxyundecyldimethoxymethylsilane, 12-(meth)acryloyloxydodecyltrimethoxysilane, and 13-(meth)acryloyloxytridecyltrimethoxysilane. One of these may be used alone, or two or more thereof can be used in appropriate combination. Among these, 2-methacryloyloxyethyltrimethoxysilane, 3-methacryloyloxypropyltrimethoxysilane, 4-methacryloyloxybutyltrimethoxysilane, 5-methacryloyloxypentyltrimethoxysilane, and 6-methacryloyloxyhexyltrimethoxysilane are preferred, and 3-methacryloyloxypropyltrimethoxysilane is more preferred, in that an adequately long alkylene group represented by —(CH₂)_(p)— results in good compatibility with the polymerizable monomers in the self-adhesive composite resin and allows the content of the filler (d) comprised in the self-adhesive dental composite resin to be sufficiently increased, and that an adequately short alkylene group represented by —(CH₂)_(p)— does not overly enhance the hydrophobicity and the bond strength is increased.

The organosilazane (B) is required to be bonded by a deammoniation reaction to the hydroxy group existing on the surface of the filler (d) and hydroxy group derived from the silane coupling agent (A). It is preferable to use the organosilazane (B) having a small molecular weight. Specific examples of the organosilazane (B) include: hexaethyldisilazane, hexa-n-propyldisilazane, hexaisopropyldisilazane, 1,1,2,2-tetramethyl-3,3-diethyldisilazane, 1,1,3,3-tetramethyldisilazane, 1,1,1,3,3,3-hexamethyldisilazane, and 1,1,1,3,3-pentamethyldisilazane. Preferred examples thereof include 1,1,3,3-tetramethyldisilazane, 1,1,1,3,3,3-hexamethyldisilazane, and 1,1,1,3,3-pentamethyldisilazane.

In the filler (d), the amount of the silane coupling agent (A) used for the treatment is preferably 0.5 to 15 parts by mass, more preferably 1 to 10 parts by mass, and particularly preferably 2 to 8 parts by mass, with respect to 100 parts by mass of the filler (d) yet to be surface-treated. If the amount of the silane coupling agent (A) used for the treatment is less than 0.5 parts by mass, the polymerizable group cannot be sufficiently imparted to the surface of the filler (d) and thus the mechanical strength may decrease.

In the surface treatment of the filler (d), the molar ratio between the silane coupling agent (A) and the organosilazane (B) is preferably [silane coupling agent (A)]:[organosilazane (B)]=1:1 to 1:20, and more preferably 1:2 to 1:10. If the molar amount of the organosilazane (B) is smaller than that of the silane coupling agent (A), aggregation may progress in the paste and the transparency may not be ensured during a storage term. If the molar amount of the organosilazane (B) is more than 20 mol with respect to 1 mol of the silane coupling agent (A), the hydrophobicity may be increased and sufficient bond strength may be unachievable.

In the surface treatment, a polymerization inhibitor may be added to reduce polymerization of the silane coupling agent (A). The polymerization inhibitor used can be a known polymerization inhibitor such as 3,5-dibutyl-4-hydroxytoluene (BHT) or p-methoxyphenol (methoquinone).

It is preferable that the surface treatment agent used in the surface treatment of the filler (d) consist essentially of the silane coupling agent (A) represented by the formula (1) and organosilazane (B) represented by the formula (2). If the surface treatment agent consists essentially of the silane coupling agent (A) and organosilazane (B), the content of a surface treatment agent component other than the silane coupling agent (A) and organosilazane (B) is less than 1.0 mass %, preferably less than 0.5 mass %, and more preferably less than 0.1 mass %.

Furthermore, the filler (d) is preferably solidified after undergoing the surface treatment. The solidification of the filler (d) is a step in which the filler (d) having undergone the surface treatment is precipitated using a mineral acid and the precipitate is washed with water and/or dehydrated (e.g., dried) to obtain solids of the filler (d). As previously described, a common filler surface-treated with a silane coupling agent (A) alone aggregates very easily, and it is thus very difficult to redisperse such a filler once the filler is solidified. However, since the filler (d) of the present invention is unlikely to aggregate, the filler (d) in a solid state is unlikely to aggregate. Even if the filler (d) of the present invention aggregates, redispersion is easy. As previously described, the filler (d) containing a small amount of ionic impurities such as an alkali metal can be easily produced by washing the filler (d) with water. The use of the filler (d) containing a small amount of ionic impurities makes it possible to maintain the above-described repulsion between the alkyl groups for a longer time and high transparency of the paste for a longer time. It is also possible to further reduce possible occurrence of an interaction between the ionic impurities and, for example, a proton (H+) yielded from the acid group-containing (meth)acrylic polymerizable monomer (a), a hydroxy group (—OH) contained in another polymerizable monomer, or a very small amount of the remaining silanol group on the filler surface, and to further reduce changes in transparency and properties of the paste. In the washing step, the washing is preferably repeated until the electric conductivity of extract water (for example, water in which the filler (d) was immersed at 121° C. for 24 hours) of the filler (d) reaches 50 μS/cm or less.

Examples of the mineral acid used in the solidification include inorganic acids such as hydrochloric acid, nitric acid, sulfuric acid, and phosphoric acid, and hydrochloric acid is particularly preferred. The mineral acid may be used as it is, and is preferably used in the form of an aqueous mineral acid solution. The concentration of the mineral acid in the aqueous mineral acid solution is preferably 0.1 mass % or more and more preferably 0.5 mass % or more. The amount of the aqueous mineral acid solution can be about 6 to 12 times larger with respect to the mass of the filler (d) to be washed.

The washing with the aqueous mineral acid solution can be performed a plurality of times. In the washing with the aqueous mineral acid solution, the filler (d) is preferably immersed in the aqueous mineral acid solution, followed by stirring. The filler (d) immersed may be left for 1 to 24 hours or even about 72 hours. The stirring may be continued or may not be continued while the filler (d) is left. The washing in a mineral acid-containing liquid can also be performed under heating to ordinary temperature or higher. Thereafter, the filler (d) is collected by filtration and then washed with water. Water used in the washing preferably contains no ions (for example, 1 ppm or less on a mass basis) of, for example, an alkali metal. Preferred examples include ion-exchange water, distilled water, and pure water. In the washing with water, as is the case for the washing with the aqueous mineral acid solution, the filler (d) may be dispersed and suspended, followed by collection by filtration. Alternatively, water may continuously go through the filler (d) collected. The end of the washing with water may be determined from the above-described electric conductivity of extract water. Alternatively, the end of the washing with water may be when the concentration of an alkali metal in discharged water resulting from the washing of the filler (d) reaches 1 ppm or less, or may be when the concentration of an alkali metal in extract water reaches 5 ppm or less. The washing with water can also be performed under heating to ordinary temperature or higher.

The filler (d) can be dried in a conventional manner. For example, the filler (d) is heated, or left under reduced pressure (vacuum). A heating apparatus and pressure reducing apparatus are not particularly limited, and known apparatuses can be used.

Except for drying, the following method can be used as a method for dehydrating the filler (d): After an aqueous organic solvent having a boiling point higher than that of water is added to the filler (d) containing water, a mixture material soluble in the aqueous organic solvent is mixed in the aqueous organic solvent, and water is removed. Examples of the aqueous organic solvent include propylene glycol monomethyl ether (propylene glycol-1-methyl ether having a boiling point around 119° C.; propylene glycol-2-methyl ether having a boiling point around 130° C.), butanol (having a boiling point of 117.7° C.), N-methyl-2-pyrrolidone (having a boiling point around 204° C.), γ-butyrolactone (having a boiling point around 204° C.).

The filler of the self-adhesive dental composite resin of the present invention may consist essentially of the filler (d). When the filler of the self-adhesive dental composite resin “consists essentially of the filler (d)”, the content of a filler other than the filler (d) is less than 1.5 mass %, preferably less than 1.0 mass %, more preferably less than 0.1 mass %, and even more preferably less than 0.01 mass %.

Next, the acid group-containing (meth)acrylic polymerizable monomer (a) used in the present invention will be described. In the present invention, the (meth)acrylic polymerizable monomer refers to a (meth)acrylate polymerizable monomer and/or (meth)acrylamide polymerizable monomer.

The acid group-containing (meth)acrylic polymerizable monomer (a) is an essential component for the self-adhesive dental composite resin of the present invention to exhibit adhesiveness. The acid group-containing (meth)acrylic polymerizable monomer (a) has the effect of demineralizing tooth structures. The acid group-containing (meth)acrylic polymerizable monomer (a) is a polymerizable monomer having at least one acid group such as a phosphoric group, phosphonic group, pyrophosphoric group, carboxylic group, or sulfonic acid group and having at least one polymerizable group such as an acryloyl group, methacryloyl group, acrylamide group, or methacrylamide group. In view of adhesion to tooth structures, the acid group-containing (meth)acrylic polymerizable monomer (a) is preferably a monofunctional monomer having any one of acryloyl, methacryloyl, acrylamide, and methacrylamide groups as a polymerizable group. Specific examples thereof are as follows.

Examples of the phosphoric acid group-containing (meth)acrylic polymerizable monomer include: phosphoric acid group-containing monofunctional (meth)acrylate compounds such as 2-(meth)acryloyloxyethyl dihydrogen phosphate, 3-(meth)acryloyloxypropyl dihydrogen phosphate, 4-(meth)acryloyloxybutyl dihydrogen phosphate, 5-(meth)acryloyloxypentyl dihydrogen phosphate, 6-(meth)acryloyloxyhexyl dihydrogen phosphate, 7-(meth)acryloyloxyheptyl dihydrogen phosphate, 8-(meth)acryloyloxyoctyl dihydrogen phosphate, 9-(meth)acryloyloxynonyl dihydrogen phosphate, 10-(meth)acryloyloxydecyl dihydrogen phosphate, 11-(meth)acryloyloxyundecyl dihydrogen phosphate, 12-(meth)acryloyloxydodecyl dihydrogen phosphate, 16-(meth)acryloyloxyhexadecyl dihydrogen phosphate, 20-(meth)acryloyloxyeicosyl dihydrogen phosphate, 2-(meth)acryloyloxyethylphenyl hydrogen phosphate, 2-(meth)acryloyloxyethyl-2-bromoethyl hydrogen phosphate, 2-(meth)acryloyloxyethyl-(4-methoxyphenyl) hydrogen phosphate, and 2-(meth)acryloyloxypropyl-(4-methoxyphenyl) hydrogen phosphate; their acid chlorides, alkali metal salts, ammonium salts, and amine salts; phosphoric acid group-containing difunctional (meth)acrylate compounds such as bis[2-(meth)acryloyloxyethyl] hydrogen phosphate, bis[4-(meth)acryloyloxybutyl]hydrogen phosphate, bis[6-(meth)acryloyloxyhexyl] hydrogen phosphate, bis[8-(meth)acryloyloxyoctyl] hydrogen phosphate, bis[9-(meth)acryloyloxynonyl]hydrogen phosphate, bis[10-(meth)acryloyloxydecyl] hydrogen phosphate, and 1,3-di(meth)acryloyloxypropyl dihydrogen phosphate; and their acid chlorides, alkali metal salts, ammonium salts, and amine salts.

Examples of the phosphonic acid group-containing (meth)acrylic polymerizable monomer include 2-(meth)acryloyloxyethylphenyl phosphonate, 5-(meth)acryloyloxypentyl-3-phosphonopropionate, 6-(meth)acryloyloxyhexyl-3-phosphonopropionate, 10-(meth)acryloyloxydecyl-3-phosphonopropionate, 6-(meth)acryloyloxyhexylphosphonoacetate, 10-(meth)acryloyloxydecylphosphonoacetate, and their acid chlorides, alkali metal salts, ammonium salts, and amine salts.

Examples of the pyrophosphoric acid group-containing (meth)acrylic polymerizable monomer include bis[2-(meth)acryloyloxyethyl] pyrophosphate, bis[4-(meth)acryloyloxybutyl] pyrophosphate, bis[6-(meth)acryloyloxyhexyl]pyrophosphate, bis[8-(meth)acryloyloxyoctyl] pyrophosphate, bis[10-(meth)acryloyloxydecyl] pyrophosphate, and their acid chlorides, alkali metal salts, ammonium salts, and amine salts.

Examples of the carboxylic acid group-containing (meth)acrylic polymerizable monomer include (meth)acrylic acid, 4-[2-[(meth)acryloyloxy]ethoxycarbonyl]phthalic acid, 4-(meth)acryloyloxyethyltrimellitic acid, 4-(meth)acryloyloxybutyloxycarbonylphthalic acid, 4-(meth)acryloyloxyhexyloxycarbonylphthalic acid, 4-(meth)acryloyloxyoctyloxycarbonylphthalic acid, 4-(meth)acryloyloxydecyloxycarbonylphthalic acid, their acid anhydrides, 5-(meth)acryloylaminopentylcarboxylic acid, 6-(meth)acryloyloxy-1,1-hexanedicarboxylic acid, 8-(meth)acryloyloxy-1,1-octanedicarboxylic acid, 10-(meth)acryloyloxy-1,1-decanedicarboxylic acid, 11-(meth)acryloyloxy-1,1-undecanedicarboxylic acid, and their acid chlorides, alkali metal salts, ammonium salts, and amine salts.

Examples of the sulfonic acid group-containing (meth)acrylic polymerizable monomer include 2-(meth)acrylamide-2-methylpropanesulfonic acid, 2-sulfoethyl (meth)acrylate, and their acid chlorides, alkali metal salts, ammonium salts and amine salts.

Among the examples of the acid group-containing (meth)acrylic polymerizable monomer (a), the phosphoric acid group-containing (meth)acrylic polymerizable monomer, pyrophosphoric acid group-containing (meth)acrylic polymerizable monomer, and carboxylic acid group-containing (meth)acrylic polymerizable monomer are preferred since such monomers provide better bond strength to tooth structures. The phosphoric acid group-containing (meth)acrylic polymerizable monomer and carboxylic acid group-containing (meth)acrylic polymerizable monomer are particularly preferred. Among these, a phosphoric acid group-containing monofunctional (meth)acrylate polymerizable monomer having as the main chain of the molecule a C₆ to C₂₀ alkyl group or C₆ to C₂₀ alkylene group and carboxylic acid group-containing (meth)acrylate polymerizable monomer having as the main chain of the molecule a C₆ to C₂₀ alkyl group or C₆ to C₂₀ alkylene group are more preferred, and a phosphoric acid group-containing monofunctional (meth)acrylate polymerizable monomer having as the main chain of the molecule a C₈ to C₂₀ alkylene group is even more preferred. Preferred are 10-methacryloyloxydecyl dihydrogen phosphate, 4-(meth)acryloyloxyethyltrimellitic acid, and 4-(meth)acryloyloxyethyltrimellitic acid anhydride, and most preferred are 10-methacryloyloxydecyl dihydrogen phosphate.

As the acid group-containing (meth)acrylic polymerizable monomer (a), one of the above monomers may be contained alone, or two or more thereof may be contained in combination. The content of the acid group-containing (meth)acrylic polymerizable monomer (a) is not particularly limited as long as the effect of the present invention can be obtained. In order to obtain higher bond strength, the content of the acid group-containing (meth)acrylic polymerizable monomer (a) is preferably in the range of 1 to 40 parts by mass, more preferably in the range of 2 to 20 parts by mass, and most preferably in the range of 4 to 20 parts by mass, in 100 parts by mass of the total polymerizable monomer components. In the present specification, the content of a polymerizable monomer in 100 parts by mass of the total polymerizable monomer components refers to the content (mass %) of the polymerizable monomer in 100 mass % of the sum of the amounts of the polymerizable monomer components. Thus, the sum of the amounts of the polymerizable monomer components does not exceed 100 parts by mass.

Next, the polyfunctional (meth)acrylic polymerizable monomer (b) containing no acid group and used in the present invention will be described. The polyfunctional (meth)acrylic polymerizable monomer (b) containing no acid group has no acid group and has at least two polymerizable groups per molecule. The polyfunctional (meth)acrylic polymerizable monomer (b) containing no acid group has the effect of improving the handling properties or mechanical strength of the self-adhesive dental composite resin of the present invention. Examples of the polyfunctional (meth)acrylic polymerizable monomer (b) containing no acid group include difunctional aromatic polymerizable monomers, difunctional aliphatic polymerizable monomers, and tri- or higher-functional polymerizable monomers.

Examples of the difunctional aromatic polymerizable monomer include difunctional (meth)acrylate compounds such as 2,2-bis((meth)acryloyloxyphenyl)propane, 2,2-bis[4-(3-(meth)acryloyloxy-2-hydroxypropoxy)phenyl]propane, 2,2-bis(4-(meth)acryloyloxyethoxyphenyl)propane, 2,2-bis(4-(meth)acryloyloxypolyethoxyphenyl)propane (having an average number of moles of added ethoxy groups of 2.6), 2,2-bis(4-(meth)acryloyloxydiethoxyphenyl)propane, 2,2-bis(4-(meth)acryloyloxytriethoxyphenyl)propane, 2,2-bis(4-(meth)acryloyloxytetraethoxyphenyl)propane, 2,2-bis(4-(meth)acryloyloxyp entaethoxyphenyl)propane, 2,2-bis(4-(meth)acryloyloxydipropoxyphenyl)propane, 2-(4-(meth)acryloyloxydiethoxyphenyl)-2-(4-(meth)acryloyloxyethoxyphenyl)propane, 2-(4-(meth)acryloyloxydiethoxyphenyl)-2-(4-(meth)acryloyloxytriethoxyphenyl)propane, 2-(4-(meth)acryloyloxydipropoxyphenyl)-2-(4-(meth)acryloyloxytriethoxyphenyl)propane, 2,2-bis(4-(meth)acryloyloxypropoxyphenyl)propane, and 2,2-bis(4-(meth)acryloyloxyisopropoxyphenyl)propane.

Examples of the difunctional aliphatic polymerizable monomer include difunctional (meth)acrylate compounds such as glycerol di(meth)acrylate, ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, propylene glycol di(meth)acrylate, butylene glycol di(meth)acrylate, neopentyl glycol di(meth)acrylate, 1,3-butanediol di(meth)acrylate, 1,5-pentanediol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, 1,10-decanediol di(meth)acrylate, 2,2,4-trimethylhexamethylene bis(2-carbamoyloxyethyl) di(meth)acrylate, and 1,2-bis(3-methacryloyloxy-2-hydroxypropoxy)ethane.

Examples of the tri- or higher-functional polymerizable monomer include tri- or higher-functional (meth)acrylate compounds such as trimethylolpropane tri(meth)acrylate, trimethylolethane tri(meth)acrylate, trimethylolmethane tri(meth)acrylate, pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol penta(meth)acrylate, N,N′-(2,2,4-trimethylhexamethylene)bis[2-(aminocarboxy)propane-1,3-diol]tetra(meth)acrylate, and 1,7-diacryloyloxy-2,2,6,6-tetra(meth)acryloyloxymethyl-4-oxaheptane. Among these, N,N′-(2,2,4-trimethylhexamethylene)bis[2-(aminocarboxy)propane-1,3-diol]tetramethacrylate is preferred.

Among the examples of the polyfunctional (meth)acrylic polymerizable monomer (b) containing no acid group, the difunctional aromatic polymerizable monomer and difunctional aliphatic polymerizable monomer are preferably used in view of the mechanical strength or handling properties. Preferred examples of the difunctional aromatic polymerizable monomer are 2,2-bis[4-(3-(methacryloyloxy-2-hydroxypropoxy)phenyl]propane (commonly known as “Bis-GMA”) and 2,2-bis(4-methacryloyloxypolyethoxyphenyl)propane (preferably having an average number of moles of added ethoxy groups of 2.6, commonly known as “D-2.6E”). Preferred examples of the difunctional aliphatic polymerizable monomer are glycerol di(meth)acrylate, triethylene glycol diacrylate, triethylene glycol dimethacrylate (commonly known as “TEGDMA”), neopentyl glycol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, 1,10-decanediol di(meth)acrylate, 1,2-bis[3-methacryloyloxy-2-hydroxypropoxy]ethane, and 2,2,4-trimethylhexamethylenebis(2-carbamoyloxyethyl) dimethacrylate (commonly known as “UDMA”).

Among the examples of the polyfunctional (meth)acrylic polymerizable monomer (b) containing no acid group, Bis-GMA, D-2.6E, TEGDMA, and UDMA are more preferred, and Bis-GMA, UDMA, and TEGDMA are even more preferred.

As the polyfunctional (meth)acrylic polymerizable monomer (b) containing no acid group, one of the above monomers may be contained alone, or two or more thereof may be contained in combination. The content of the polyfunctional (meth)acrylic polymerizable monomer (b) containing no acid group is not particularly limited as long as the effect of the present invention can be obtained. In order to provide the dental composition (self-adhesive dental composite resin) with high penetrability into a tooth structure, excellent bond strength, and sufficient strength, the content of the polyfunctional (meth)acrylic polymerizable monomer (b) containing no acid group is preferably in the range of 30 to 95 parts by mass, more preferably in the range of 40 to 90 parts by mass, even more preferably in the range of 50 to 85 parts by mass, and most preferably in the range of 60 to 80 parts by mass, in 100 parts by mass of the total polymerizable monomer components in the self-adhesive dental composite resin.

The self-adhesive dental composite resin of the present invention may further comprise an amide proton-containing polyfunctional (meth)acrylamide polymerizable monomer (e) as a polymerizable monomer component. The polyfunctional (meth)acrylamide polymerizable monomer (e) containing at least one amide proton has high hydrophilicity owing to the at least one amide proton, penetrates easily into the collagen layer of dentin, and shows very high curability together with other components of the self-adhesive dental composite resin owing to a plurality of polymerizable groups per molecule. These contribute to higher bond strength to dentin.

Examples of the polyfunctional (meth)acrylamide polymerizable monomer (e) include a polyfunctional (meth)acrylamide polymerizable monomer (e1) represented by the following general formula (3), polyfunctional (meth)acrylamide polymerizable monomer (e2) represented by the following general formula (4), and polyfunctional (meth)acrylamide polymerizable monomer (e3) represented by the following general formula (5).

(In the formula, R¹⁰, R¹¹, and R¹² are each independently a hydrogen atom or methyl group, s is an integer of 1 to 6, X¹ and X² are each independently an optionally substituted C₁ to C₈ linear or branched alkylene group.)

(In the formula, R¹³ and R¹⁴ are each independently a hydrogen atom or methyl group, t is 2 or 3, and X³ and X⁴ are each independently an optionally substituted C₁ to C₈ linear or branched alkylene group.)

(In the formula, Z is an optionally substituted C₁ to C₈ linear or branched aliphatic or aromatic group, and the aliphatic group may be interrupted by at least one linking group selected from the group consisting of —O—, —S—, —CO—, —CO—O—, —O—CO—, —NR¹⁵—, —CO—NR¹⁵—, —NR¹⁵—CO—, —CO—O—NR¹⁵—, —O—CONR¹⁵—, and —NR¹⁵—CO—NR¹⁵—. R¹⁵ represents a hydrogen atom or optionally substituted C₁ to C₈ linear or branched aliphatic group.)

R¹⁰, R¹¹, R¹², R¹³, and R¹⁴ are each preferably a hydrogen atom in view of adhesion to tooth structures and polymerization curability. s is preferably an integer of 1 to 4, more preferably an integer of 1 to 3, and particularly preferably 1 or 2. t is preferably 3.

Examples of the optionally substituted C₁ to C₈ linear or branched alkylene group represented by X¹, X², X³, and X⁴ include methylene, methylmethylene, ethylene, 1-methylethylene, 2-methylethylene, trimethylene, 1-ethylethylene, 2-ethylethylene, 1,2-dimethylethylene, 2,2-dimethylethylene, 1-methyltrimethylene, 2-methyltrimethylene, 3-methyltrimethylene, tetramethylene, 1-propylethylene, 2-propylethylene, 1-ethyl-1-methylethylene, 1-ethyl-2-methylethylene, 1,1,2-trimethylethylene, 1,2,2-trimethylethylene, 1-ethyltrimethylene, 2-ethyltrimethylene, 3-ethyltrimethylene, 1,1-dimethyltrimethylene, 1,2-dimethyltrimethylene, 1,3-dimethyltrimethylene, 2,3-dimethyltrimethylene, 3,3-dimethyltrimethylene, 1-methyltetramethylene, 2-methyltetramethylene, 3-methyltetramethylene, 4-methyltetramethylene, pentamethylene, 1-butylethylene, 2-butylethylene, 1-methyl-1-propylethylene, 1-methyl-2-propylethylene, 2-methyl-2-propylethylene, 1,1-diethylethylene, 1,2-diethylethylene, 2,2-diethylethylene, 1-ethyl-1,2-dimethylethylene, 1-ethyl-2,2-dimethylethylene, 1-methylpentamethylene, 2-methylpentamethylene, 3-methylpentamethylene, 4-methylpentamethylene, 5-methylpentamethylene, and hexamethylene groups.

Preferred examples of the substituent in X¹, X², X³, and X⁴ include a halogen atom (fluorine, chlorine, bromine, or iodine atom), carboxy group, hydroxy group, amino group, amino group mono- or di-substituted by a C₁ to C₈ alkyl group, acyl group, acyloxy group, amide group, C₂ to C₈ alkoxycarbonyl group, C₁ to C₈ alkoxy group, C₁ to C₈ alkylthio group, and C₁ to C₈ alkyl group, and more preferred examples include a halogen atom (fluorine, chlorine, bromine, or iodine atom) and C₁ to C₈ alkyl group. Example of the alkyl group include methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, 2-methylpropyl, tert-butyl, n-pentyl, isopentyl, n-hexyl, n-heptyl, 2-methylhexyl, and n-octyl groups. The alkyl group is preferably a linear or branched C₁ to C₄ alkyl group. The number of the substituents is not particularly limited. The number of the/-substituents may be about 1 to 8, and is preferably 1, 2, or 3.

The optionally substituted C₁ to C₈ aliphatic group represented by Z may be a saturated aliphatic group (such as an alkylene group or cycloalkylene group (for example, 1,4-cyclohexylene group)) or unsaturated aliphatic group (such as an alkenylene group or alkynylene group), and is preferably a saturated aliphatic group (alkylene group) in view of availability, ease of production, and chemical stability. Z is preferably an optionally substituted, linear or branched C₁ to C₄ aliphatic group and more preferably an optionally substituted, linear or branched C₂ to C₄ aliphatic group in view of adhesion to tooth structures and polymerization curability. Examples of the C₁ to C₈ alkylene group are the same as those of X¹, X², X³, and X⁴.

Examples of the optionally substituted aromatic group represented by Z include an aryl group and aromatic heterocyclic group. As the aromatic group, an aryl group is more preferred than an aromatic heterocyclic group. The hetero ring of the aromatic heterocyclic group is generally unsaturated. The aromatic hetero ring is preferably a 5-membered or 6-membered ring. As the aryl group, for example, a phenyl group is preferred. Examples of the aromatic heterocyclic group include furan, thiophene, pyrrole, oxazole, isoxazole, thiazole, isothiazole, imidazole, pyrazole, furazan, triazole, pyran, pyridine, pyridazine, pyrimidine, pyrazine, and 1,3,5-triazine groups. Among these aromatic groups, a phenyl group is particularly preferred.

The aliphatic group represented by R¹⁵ may be either a saturated aliphatic group (alkyl group) or unsaturated aliphatic group (alkenyl or alkynyl group), and is preferably a saturated aliphatic group (alkyl group) in view of availability, ease of production, and chemical stability. Examples of the alkyl group include C₁ to C₈ alkyl groups which are identical to those described as the substituents in X¹, X², X³, and X⁴. R¹⁵ is more preferably a hydrogen atom or optionally substituted linear or branched C₁ to C₄ alkyl group and even more preferably a hydrogen atom or optionally substituted linear or branched C₁ to C₃ alkyl group.

The aliphatic group represented by Z may be interrupted by the at least one linking group described above. That is, the at least one linking group may be introduced into the aliphatic group. The number of the linking groups interrupting the aliphatic group represented by Z is not particularly limited, and may be about 1 to 10, preferably 1, 2, or 3, and more preferably 1 or 2. In the formula (5), the aliphatic group represented by Z is preferably not interrupted by two or more continuous linking groups. That is, the linking groups are preferably not adjacent to each other. The linking group is more preferably at least one linking group selected from the group consisting of —O—, —S—, —CO—, —CO—O—, —O—CO—, —NH—, —CO—NH—, —NH—CO—, —CO—O—NH—, —O—CO—NH—, and —NH—CO—NH— and even more preferably at least one linking group selected from the group consisting of —O—, —S—, —CO—, —NH—, —CO—NH—, and —NH—CO—.

Specific examples of the polyfunctional (meth)acrylamide polymerizable monomer (e1) represented by the formula (3) include, but are not particularly limited to, the following.

Among these, in view of adhesion to tooth structures and polymerization curability, the compound (e1-1), compound (e1-3), compound (e1-5), and compound (e1-7) are preferred, and the compound (e1-1) and compound (e1-5) are more preferred. The compound (e1-5) is most preferred because of its high hydrophilicity responsible for penetration into the collagen layer of dentin.

Specific examples of the polyfunctional (meth)acrylamide polymerizable monomer (e2) represented by the formula (4) include, but are not particularly limited to, the following.

Among these, in view of adhesion to tooth structures and polymerization curability, the compound (e2-1), compound (e2-3), compound (e2-5), and compound (e2-7) are preferred, and the compound (e2-1) and compound (e2-3) are more preferred. The compound (e2-1) is most preferred because of its high hydrophilicity responsible for penetration into the collagen layer of dentin.

Specific examples of the polyfunctional (meth)acrylamide polymerizable monomer (e3) (which may hereinafter be referred to as an asymmetric polyfunctional (meth)acrylamide polymerizable monomer (e3)) represented by the formula (5) include, but are not particularly limited to, the following.

Among these, N-methacryloyloxyethyl acrylamide, N-methacryloyloxypropyl acrylamide, N-methacryloyloxybutyl acrylamide, N-(1-ethyl-(2-methacryloyloxy)ethyl)acrylamide, and N-(2-(2-methacryloyloxyethoxy)ethyl)acrylamide are more preferred in view of adhesion to tooth structures and polymerization curability. N-methacryloyloxyethyl acrylamide and N-methacryloyloxypropyl acrylamide are most preferred because of its high hydrophilicity responsible for penetration into the collagen layer of dentin.

As the polyfunctional (meth)acrylamide polymerizable monomer (e) containing at least one amide proton, one of these examples may be used alone, or two or more thereof may be used in combination. For example, the polyfunctional (meth)acrylamide polymerizable monomer (e3) and one or more polymerizable monomers selected from the group consisting of the polyfunctional (meth)acrylamide polymerizable monomer (e1) and polyfunctional (meth)acrylamide polymerizable monomer (e2) may be combined. The content of the polyfunctional (meth)acrylamide polymerizable monomer (e) is not particularly limited as long as the effect of the present invention can be obtained. The content of the polyfunctional (meth)acrylamide polymerizable monomer (e) is preferably in the range of 0.5 to 30 parts by mass, more preferably in the range of 2 to 25 parts by mass, and most preferably in the range of 3 to 20 parts by mass, in 100 parts by mass of the total polymerizable monomer components in the self-adhesive dental composite resin.

The self-adhesive dental composite resin of the present invention may further comprise or may not comprise a hydrophilic monofunctional polymerizable monomer (f) as a polymerizable monomer component. The hydrophilic monofunctional polymerizable monomer (f) refers to a monofunctional polymerizable monomer having a solubility of 5 mass % or more in water at 25° C. and being other than (a), (b), and (e). The solubility in water at 25° C. is preferably 10 mass % or more and more preferably 15 mass % or more. The addition of the hydrophilic monofunctional polymerizable monomer (e) achieves higher bond strength to dentin.

The hydrophilic monofunctional polymerizable monomer (f) has at least one hydrophilic group such as hydroxy, oxymethylene, oxyethylene, oxypropylene, and amide groups. Examples of the hydrophilic monofunctional polymerizable monomer (f) include: hydrophilic monofunctional (meth)acrylate polymerizable monomers such as 2-hydroxyethyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 1,3-dihydroxypropyl (meth)acrylate, 2,3-dihydroxypropyl (meth)acrylate, and 2-trimethylammoniumethyl (meth)acrylchloride; and hydrophilic monofunctional (meth)acrylamide polymerizable monomers such as N-methylol (meth)acrylamide, N-hydroxyethyl (meth)acrylamide, N,N-bis(dihydroxyethyl) (meth)acrylamide, N-methoxymethyl (meth)acrylamide, N-ethoxymethyl (meth)acrylamide, diacetone (meth)acrylamide, 4-(meth)acryloylmorpholine, N-trihydroxymethyl-N-methyl (meth)acrylamide, and monofunctional (meth)acrylamide polymerizable monomers represented by the following general formula (6).

(In the formula, R¹⁶ and R¹⁷ are each independently an optionally substituted, linear or branched C₁ to C₃ alkyl group, and R¹⁸ is a hydrogen atom or methyl group.)

Examples of the substituent in R¹⁶ and R¹⁷ are the same as those in X¹, X², X³, and X⁴. Examples of the C₁ to C₃ alkyl group represented by R¹⁶ and R¹⁷ include methyl, ethyl, n-propyl, and isopropyl groups.

Among these examples of the hydrophilic monofunctional polymerizable monomer (f), in view of adhesion to tooth structures, 2-hydroxyethyl (meth)acrylate, 2,3-dihydroxypropyl (meth)acrylate, diacetone (meth)acrylamide, and the hydrophilic monofunctional (meth)acrylamide polymerizable monomers represented by the general formula (6) are preferred, and the monofunctional (meth)acrylamide polymerizable monomers represented by the general formula (6) are more preferred. As the hydrophilic monofunctional polymerizable monomer (f), one of the above monomers may be used alone, or two or more thereof may be used in combination.

Among the monofunctional (meth)acrylamide polymerizable monomers represented by the general formula (6), N,N-dimethylacrylamide and N,N-diethylacrylamide are more preferred, and N,N-diethylacrylamide is most preferred, in view of storage stability.

The content of the hydrophilic monofunctional polymerizable monomer (f) of the present invention is not particularly limited as long as the effect of the present invention can be obtained. In order to obtain a sufficient effect on improvement of the bond strength and sufficient mechanical strength, the content of the hydrophilic monofunctional polymerizable monomer (f) is preferably in the range of 1 to 30 parts by mass, more preferably in the range of 2 to 28 parts by mass, even more preferably in the range of 5 to 25 parts by mass, and particularly preferably in the range of 7 to 20 parts by mass, in 100 parts by mass of the total polymerizable monomer components in the self-adhesive dental composite resin.

As long as the effect of the present invention can be obtained, the self-adhesive dental composite resin of the present invention may comprise a polymerizable monomer (g) in addition to the acid group-containing (meth)acrylic polymerizable monomer (a), polyfunctional (meth)acrylic polymerizable monomer (b) containing no acid group, amide proton-containing polyfunctional (meth)acrylamide polymerizable monomer (e), and hydrophilic monofunctional polymerizable monomer (f) in order to improve the bond strength, handling properties, and mechanical strength. Examples of the polymerizable monomer (g) include a hydrophilic polyfunctional (meth)acrylate polymerizable monomer (g1) and/or symmetric (meth)acrylamide compound (g2). The hydrophilic polyfunctional (meth)acrylate polymerizable monomer (g1) refers to a polyfunctional polymerizable monomer having a solubility of 5 mass % or more in water at 25° C. and being other than (a), (b), and (e). The solubility in water at 25° C. is preferably 10 mass % or more and more preferably 15 mass % or more. Examples of the hydrophilic polyfunctional (meth)acrylate polymeriszable monomer (g1) include pentaerythritol di(meth)acrylate, erythritol di(meth)acrylate, mannitol di(meth)acrylate, xylitol di(meth)acrylate, and sorbitol di(meth)acrylate. Examples of the symmetric (meth)acrylamide compound (g2) include N,N′-ethylenebisacrylamide and N,N′-diethyl-1,3-propylenebisacrylamide. As the polymerizable monomer (g), one of these examples may be used alone, or two or more thereof may be used in combination.

The sum of the contents of the polymerizable monomers comprised in the self-adhesive dental composite resin of the present invention is preferably less than 49.9 mass %, more preferably less than 44.5 mass %, and even more preferably less than 40.0 mass % with respect to the total mass of the self-adhesive dental composite resin. The sum of the contents of the polymerizable monomers is preferably 9.0 mass % or more, more preferably 14.0 mass % or more, and even more preferably 19.0 mass % or more with respect to the total mass of the self-adhesive dental composite resin.

The photopolymerization initiator (c) is a component that promotes polymerization curing of the self-adhesive dental composite resin. The photopolymerization initiator (c) can be selected for use from known photopolymerization initiators, among which photopolymerization initiators for dental use are preferably used. One of these may be used alone, or two or more thereof are used in appropriate combination as the photopolymerization initiator (c).

Examples of the photopolymerization initiator (c) include (bis)acylphosphine oxides, water-soluble acylphosphine oxides, thioxanthones, quaternary ammonium salts of thioxanthones, ketals, α-diketones, coumarins, anthraquinones, benzoin alkyl ether compounds, and α-aminoketone compounds.

It is preferable to use, among these examples of the photopolymerization initiator (c), at least one selected from the group consisting of (bis)acylphosphine oxides, salts thereof, α-diketones, and coumarins. The use of such a photopolymerization initiator makes it possible to obtain a self-adhesive dental composite resin that has excellent photocurability in the visible and near-ultraviolet regions and thus exhibits sufficiently high photocurability regardless of which light source among a halogen lamp, light-emitting diode (LED), and xenon lamp is used.

Examples of the acylphosphine oxides include 2,4,6-trimethylbenzoyldiphenylphosphine oxide, 2,6-dimethoxybenzoyldiphenylphosphine oxide, 2,6-dichlorobenzoyldiphenylphosphine oxide, 2,4,6-trimethylbenzoylmethoxyphenylphosphine oxide, 2,4,6-trimethylbenzoylethoxyphenylphosphine oxide, 2,3,5,6-tetramethylbenzoyldiphenylphosphine oxide, and benzoyl di-(2,6-dimethylphenyl)phosphonate. Preferred among these is 2,4,6-trimethylbenzoyldiphenylphosphine oxide.

Examples of the bisacylphosphine oxides include bis-(2,6-dichlorobenzoyl)phenylphosphine oxide, bis-(2,6-dichlorobenzoyl)-2,5-dimethylphenylphosphine oxide, bis-(2,6-dichlorobenzoyl)-4-propylphenylphosphine oxide, bis-(2,6-dichlorobenzoyl)-1-naphthylphosphine oxide, bis-(2,6-dimethoxybenzoyl)phenylphosphine oxide, bis-(2,6-dimethoxybenzoyl)-2,4,4-trimethylpentylphosphine oxide, bis-(2,6-dimethoxybenzoyl)-2,5-dimethylphenylphosphine oxide, bis-(2,4,6-trimethylbenzoyl)phenylphosphine oxide, and bis-(2,5,6-trimethylbenzoyl)-2,4,4-trimethylpentylphosphine oxide. Preferred among these is bis-(2,4,6-trimethylbenzoyl)phenylphosphine oxide.

Examples of the α-diketones include diacetyl, dibenzyl, camphorquinone, 2,3-pentadione, 2,3-octadione, 9,10-phenanthrenequinone, 4,4′-oxybenzyl, and acenaphthenequinone. Particularly preferred among these is camphorquinone, since it shows maximum absorption at a wavelength in the visible region.

Examples of the coumarin compounds include compounds disclosed in JP H09-003109 A and JP H10-245525 A, such as 3,3′-carbonylbis(7-diethylaminocoumarin), 3-(4-methoxybenzoyl)coumarin, 3-thenoylcoumarin, 3-benzoyl-5,7-dimethoxycoumarin, 3-benzoyl-7-methoxycoumarin, 3-benzoyl-6-methoxycoumarin, 3-benzoyl-8-methoxycoumarin, 3-benzoylcoumarin, 7-methoxy-3-(p-nitrobenzoyl)coumarin, 3-(p-nitrobenzoyl)coumarin, 3,5-carbonylbis(7-methoxycoumarin), 3-benzoyl-6-bromocoumarin, 3,3′-carbonylbiscoumarin, 3-benzoyl-7-dimethylaminocoumarin, 3-benzoylbenzo[f]coumarin, 3-carboxycoumarin, 3-carboxy-7-methoxycoumarin, 3-ethoxycarbonyl-6-methoxycoumarin, 3-ethoxycarbonyl-8-methoxycoumarin, 3-acetylbenzo[f]coumarin, 3-benzoyl-6-nitrocoumarin, 3-benzoyl-7-diethylaminocoumarin, 7-dimethylamino-3-(4-methoxybenzoyl)coumarin, 7-diethylamino-3-(4-methoxybenzoyl)coumarin, 7-diethylamino-3-(4-diethylamino)coumarin, 7-methoxy-3-(4-methoxybenzoyl)coumarin, 3-(4-nitrobenzoyl)benzo[f]coumarin, 3-(4-ethoxycinnamoyl)-7-methoxycoumarin, 3-(4-dimethylaminocinnamoyl)coumarin, 3-(4-diphenylaminocinnamoyl)coumarin, 3-[(3-dimethylbenzothiazol-2-ylidene)acetyl]coumarin, 3-[(1-methylnaphto[1,2-d]thiazol-2-ylidene)acetyl]coumarin, 3,3′-carbonylbis(6-methoxycoumarin), 3,3′-carbonylbis(7-acetoxycoumarin), 3,3′-carbonylbis(7-dimethylaminocoumarin), 3-(2-benzothiazoyl)-7-(diethylamino)coumarin, 3-(2-benzothiazoyl)-7-(dibutylamino)coumarin, 3-(2-benzoimidazoyl)-7-(diethylamino)coumarin, 3-(2-benzothiazoyl)-7-(dioctylamino)coumarin, 3-acetyl-7-(dimethylamino)coumarin, 3,3′-carbonylbis(7-dibutylaminocoumarin), 3,3′-carbonyl-7-diethylaminocoumarin-7′-bis(butoxyethyl)aminocoumarin, 10-[3-[4-(dimethylamino)phenyl]-1-oxo-2-propenyl]-2,3,6,7-tetrahydro-1,1,7,7-tetramethyl-1H,5H,11H-[1]benzopyrano[6,7,8-ij]quinolizin-11-one, and 10-(2-benzothiazoyl)-2,3,6,7-tetrahydro-1,1,7,7-tetramethyl-1H,5H,11H-[1]benzopyrano[6,7,8-ij]quinolizin-11-one. Preferred among these are 3,3′-carbonylbis(7-diethylaminocoumarin) and 3,3′-carbonylbis(7-dibutylaminocoumarin).

Specific examples of water-soluble acylphosphine oxides, thioxanthones, quaternary ammonium salts of thioxanthones, ketals, anthraquinones, benzoin alkyl ether compounds, and α-aminoketone compounds include those disclosed in WO 2008/087977 A1.

The content of the photopolymerization initiator (c) is not particularly limited. In view of, for example, the curability of the resultant self-adhesive dental composite resin, the content of the photopolymerization initiator (c) is preferably 0.001 to 20 parts by mass, more preferably 0.05 to 10 parts by mass, and even more preferably 0.10 to 5 parts by mass, with respect to 100 parts by mass of the total polymerizable monomers. When the content of the photopolymerization initiator (c) is less than 0.001 parts by mass with respect to 100 parts by mass of the total polymerizable monomers, polymerization may not proceed sufficiently and thus the bond strength may be reduced. Therefore, a content of 0.05 parts by mass or more is more preferred, and a content of 0.10 parts by mass or more is even more preferred. On the other hand, when the content of the photopolymerization initiator (c) is more than 20 parts by mass with respect to 100 parts by mass of the total polymerizable monomers and the polymerizability thereof is low, sufficient bond strength may not be obtained and, furthermore, segregation from the self-adhesive dental composite resin may occur. Therefore, a content of 10 parts by mass or less is more preferred, and a content of 5 parts by mass or less is even more preferred with respect to 100 parts by mass of the total polymerizable monomers.

The self-adhesive dental composite resin of the present invention may further comprise a chemical polymerization initiator. An organic peroxide is preferably used as the chemical polymerization initiator. The organic peroxide is not particularly limited, and can be a commonly-known organic peroxide. Typical examples of the organic peroxide include ketone peroxides, hydroperoxides, diacyl peroxides, dialkyl peroxides, peroxyketals, peroxyesters, and peroxydicarbonates. Specific examples of the organic peroxides include those disclosed in WO 2008/087977 A1. As the chemical polymerization initiator, one of these examples may be used alone, or two or more thereof may be used in appropriate combination.

The self-adhesive dental composite resin of the present invention may comprise a filler (h) containing no organosilazane (B) in its surface treatment agent as long as changes in the transparency and properties of the paste and the solidification risk are not affected during long-term storage. The filler (h) is a component for imparting the X-ray opacity to the self-adhesive dental composite resin or for improving the self-adhesive dental composite resin in strength as a matrix or handling properties as a paste.

The term “X-ray opacity” as used in the present specification refers to the ability of a cured dental material distinguished from a tooth structure using a dental X-ray apparatus commonly used in conventional methods. The radiopacity of dental materials is advantageous in a particular case where the tooth condition is diagnosed by X-ray.

As the filler (h), any known filler used in dental composite resins, except for those prepared by flame pyrolysis, can be used without any limitation. Examples of the filler include: various types of glasses [containing silica as a main component and optionally containing oxides of heavy metals, boron, aluminum, etc., for example: glass powders having typical compositions, such as fused silica, quartz, soda lime silica glass, E-glass, C-glass, borosilicate glass (Pyrex (registered trademark) glass); and glass powders for dental use, such as barium glass (GM 27884 and 8235 manufactured by Schott, and E-2000 and E-3000 manufactured by Esstech, Inc.), strontium borosilicate glass (E-4000 manufactured by Esstech, Inc.), lanthanum glass ceramics (GM 31684 manufactured by Schott), and fluoroaluminosilicate glass (GM 35429, G018-091, and G018-117 manufactured by Schott)]; various types of ceramics; composite oxides such as silica-titania and silica-zirconia; diatomaceous earth; kaolin; clay minerals (such as montmorillonite); activated white clay; synthetic zeolite; mica; calcium fluoride; ytterbium fluoride; yttrium fluoride; calcium fluoride having the surface coated with silica and having a core-shell structure; ytterbium fluoride having the surface coated with silica and having a core-shell structure; yttrium fluoride having the surface coated with silica and having a core-shell structure; calcium phosphate; barium sulfate; zirconium dioxide; titanium dioxide; hydroxyapatite; calcium phosphate having the surface coated with silica and having a core-shell structure; barium sulfate having the surface coated with silica and having a core-shell structure; zirconium dioxide having the surface coated with silica and having a core-shell structure; titanium dioxide having the surface coated with silica and having a core-shell structure; and hydroxyapatite having the surface coated with silica and having a core-shell structure. One of these may be used alone, or two or more thereof can be used in combination. Among these, ytterbium fluoride having the surface coated with silica and having a core-shell structure and yttrium fluoride having the surface coated with silica and having a core-shell structure are suitable because they contribute to showing the X-ray opacity at a small amount and can be treated with the silane coupling agent (A). It is not preferable to add a filler prepared by flame pyrolysis because, in that case, thixotropy attributable to a hydroxy group or the like on the surface of such a filler having a large specific surface area is exhibited remarkably and thus a problem occurs in that the paste properties exhibited just after preparation of the paste and those exhibited after storage of the paste are greatly different. Commercially-available fillers prepared by flame pyrolysis are, for example, AEROSIL, AEROXIDE Alu C, AEROXIDE TiO₂ P 25, AEROXIDE TiO₂ P 25, VP Zirconium Oxide 3-YSZ, and VP Zirconium Oxide 3-YSZ PH, which are trade names and manufactured by Nippon Aerosil Co., Ltd.

The average particle diameter of the filler (h) is preferably 0.01 to 50.0 μm, more preferably 0.05 to 20.0 μm, even more preferably 0.08 to 10.0 μm, and particularly preferably 0.10 to 4.50 μm. When the average particle diameter of the filler (h) is within these ranges, sufficient mechanical strength can be obtained, and the paste does not become sticky and thus has good handling properties. In addition, the resultant cured product has high surface smoothness and gloss after polishing and good retention of the smoothness and gloss. In the present specification, the average particle diameter of the filler means the average particle diameter (average primary particle diameter) of the primary particles of the filler.

The average particle diameter of the filler (h) can be measured in the same manner as the method for measuring the average particle diameter of the filler (d).

Examples of the surface treatment agent of the filler (h) include at least one organometallic compound selected from the group consisting of organosilicon compounds, organotitanium compounds, organozirconium compounds, and organoaluminum compounds. When two or more organometallic compounds are used, the resultant surface-treated layer may be composed of a mixture of the two or more organometallic compounds or may have a multilayer structure composed of two or more stacked layers respectively consisting of the organometallic compounds.

Examples of the organosilicon compound include compounds represented by (R¹⁹)_(n)SiY_(4-n), wherein R¹⁹ is a substituted or unsubstituted C₁ to C₁₂ hydrocarbon group, Y is a C₁ to C₄ alkoxy group, a hydroxy group, a halogen atom, or a hydrogen atom, and n is an integer of 0, 1, 2, or 3. When there are two or more R¹⁹ and two or more Y, the two or more R¹⁹ may be the same as or different from each other, and the two or more Y may be the same as or different from each other.

Specific examples of the organosilicon compound include methyltrimethoxysilane, dimethyldimethoxysilane, phenyltrimethoxysilane, diphenyldimethoxysilane, methyltriethoxysilane, dimethyldiethoxysilane, phenyltriethoxysilane, diphenyldiethoxysilane, isobutyltrimethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, vinyltris(ß-methoxyethoxy)silane, 3,3,3-trifluoropropyltrimethoxysilane, methyl-3,3,3-trifluoropropyldimethoxysilane, ß-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropylmethyldiethoxysilane, γ-glycidoxypropyltriethoxysilane, γ-methacryloyloxypropylmethyldimethoxysilane, γ-methacryloyloxypropylmethyldiethoxysilane, N-ß-(aminoethyl)-γ-aminopropylmethyldimethoxysilane, N-ß-(aminoethyl)-γ-aminopropyltrimethoxysilane, N-ß-(aminoethyl)-γ-aminopropyltriethoxysilane, γ-aminopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, N-phenyl-γ-aminopropyltrimethoxysilane, γ-mercaptopropyltrimethoxysilane, trimethylsilanol, methyltrichlorosilane, methyldichlorosilane, dimethyldichlorosilane, trimethylchlorosilane, phenyltrichlorosilane, diphenyldichlorosilane, vinyltrichlorosilane, trimethylbromosilane, diethylsilane, vinyltriacetoxysilane, ω-(meth)acryloyloxyalkyltrimethoxysilane (the number of carbon atoms between the (meth)acryloyloxy group and the silicon atom: 3 to 12, e.g., 3-methacryloyloxypropyltrimethoxysilane), and ω-(meth)acryloyloxyalkyltriethoxysilane (the number of carbon atoms between the (meth)acryloyloxy group and the silicon atom: 3 to 12, e.g., 3-methacryloyloxypropyltriethoxysilane).

Among these, a coupling agent having a functional group copolymerizable with the above polymerizable monomer components is particularly preferably used, and examples thereof include ω-(meth)acryloyloxyalkyltrimethoxysilane (the number of carbon atoms between the (meth)acryloyloxy group and the silicon atom: 3 to 12), ω-(meth)acryloyloxyalkyltriethoxysilane (the number of carbon atoms between the (meth)acryloyloxy group and the silicon atom: 3 to 12), vinyltrimethoxysilane, vinyltriethoxysilane, vinyltriacetoxysilane, and γ-glycidoxypropyltrimethoxysilane.

Examples of the organotitanium compound include tetramethyl titanate, tetraisopropyl titanate, tetra-n-butyl titanate, butyl titanate dimer, and tetra(2-ethylhexyl) titanate.

Examples of the organozirconium compound include zirconium isopropoxide, zirconium n-butoxide, zirconium acetylacetonate, and zirconyl acetate.

Examples of the organoaluminum compound include aluminum acetylacetonate and a chelate compound of a salt of aluminum and an organic acid.

The shape of the filler (h) is not particularly limited. The shape of the filler (h) may be selected as appropriate depending on a property intended to be improved of the dental composite resin. Specifically, the filler (h) can be used in the form of a powder consisting of irregular-shaped or spherical particles. When the irregular-shaped filler (h) is used, the mechanical strength and wear resistance are particularly improved. When the spherical filler (h) is used, the surface smoothness and gloss after polishing and the retention of the smoothness and gloss are particularly improved. A commercially available filler may be used as the filler (h) of the present invention.

The content of the filler (h) is not particularly limited as long as the effect of the present invention can be obtained. The content of the filler (h) is preferably in the range of 1 to 100 parts by mass, more preferably in the range of 3 to 90 parts by mass, and particularly preferably in the range of 5 to 80 parts by mass, with respect to 100 parts by mass of the total polymerizable monomers. When the content of the filler (h) is in these ranges, both sufficient X-ray opacity or sufficient mechanical strength of the resultant cured product and sufficient paste handling properties can be obtained.

The sum of the contents of the fillers comprised in the self-adhesive dental composite resin of the present invention is preferably 50.0 mass % or more, more preferably 55.0 mass % or more, and even more preferably 59.0 mass % or more with respect to the total mass of the self-adhesive dental composite resin. The sum of the contents of the fillers is preferably 90.0 mass % or less, more preferably 85.0 mass % or less, and even more preferably 80.0 mass % or less with respect to the total mass of the self-adhesive dental composite resin. When the self-adhesive dental composite resin of the present invention comprises a filler consisting essentially of the filler (d), the above preferred sum of the contents may be the content of the filler (d).

Next, other optional components of the self-adhesive dental composite resin of the present invention will be described.

In another embodiment, the photopolymerization initiator (c) and/or chemical polymerization initiator is used in combination with a polymerization accelerator (i). Examples of the polymerization accelerator (i) include amines, sulfinic acids, salts of sulfinic acids, borate compounds, barbituric acid derivatives, triazine compounds, copper compounds, tin compounds, vanadium compounds, halogen compounds, aldehydes, thiol compounds, sulfites, hydrogen sulfites, and thiourea compounds.

The above amines are classified into aliphatic amines and aromatic amines. Examples of the aliphatic amines include: primary aliphatic amines such as n-butylamine, n-hexylamine, and n-octylamine; secondary aliphatic amines such as diisopropylamine, dibutylamine, and N-methylethanolamine; and tertiary aliphatic amines such as N-methyldiethanolamine, N-ethyldiethanolamine, N-n-butyldiethanolamine, N-lauryldiethanolamine, 2-(dimethylamino)ethyl methacrylate, N-methyldiethanolamine dimethacrylate, N-ethyldiethanolamine dimethacrylate, triethanolamine monomethacrylate, triethanolamine dimethacrylate, triethanolamine trimethacrylate, triethanolamine, trimethylamine, triethylamine, and tributylamine. Among these, tertiary aliphatic amines are preferred in view of the curability and storage stability of the self-adhesive dental composite resin, and in particular, N-methyldiethanolamine and triethanolamine are more preferably used.

Examples of the aromatic amines include N,N-bis(2-hydroxyethyl)-3,5-dimethylaniline, N,N-bis(2-hydroxyethyl)-p-toluidine, N,N-bis(2-hydroxyethyl)-3,4-dimethylaniline, N,N-bis(2-hydroxyethyl)-4-ethylaniline, N,N-bis(2-hydroxyethyl)-4-isopropylaniline, N,N-bis(2-hydroxyethyl)-4-t-butylaniline, N,N-bis(2-hydroxyethyl)-3,5-diisopropylaniline, N,N-bis(2-hydroxyethyl)-3,5-di-t-butylaniline, N,N-dimethylaniline, N,N-dimethyl-p-toluidine, N,N-dimethyl-m-toluidine, N,N-diethyl-p-toluidine, N,N-dimethyl-3,5-dimethylaniline, N,N-dimethyl-3,4-dimethylaniline, N,N-dimethyl-4-ethylaniline, N,N-dimethyl-4-isopropylaniline, N,N-dimethyl-4-t-butylaniline, N,N-dimethyl-3,5-di-t-butylaniline, ethyl 4-(N,N-dimethylamino)benzoate, methyl 4-(N,N-dimethylamino)benzoate, propyl 4-(N,N-dimethylamino)benzoate, n-butoxyethyl 4-(N,N-dimethylamino)benzoate, 2-[methacryloyloxy]ethyl 4-(N,N-dimethylamino)benzoate, 4-(N,N-dimethylamino)benzophenone, and butyl 4-(N,N-dimethylamino)benzoate. Among these, at least one selected from the group consisting of N,N-bis(2-hydroxyethyl)-p-toluidine, ethyl 4-(N,N-dimethylamino)benzoate, n-butoxyethyl 4-(N,N-dimethylamino)benzoate, and 4-(N,N-dimethylamino)benzophenone is preferably used in view of their ability to impart high curability to the self-adhesive dental composite resin.

Specific examples of the sulfinic acids, salts of sulfinic acids, borate compounds, barbituric acid derivatives, triazine compounds, copper compounds, tin compounds, vanadium compounds, halogen compounds, aldehydes, thiol compounds, sulfites, hydrogen sulfites, and thiourea compounds include those disclosed in WO 2008/087977 A1.

As the polymerization accelerator (i), one of these examples may be contained alone, or two or more thereof may be contained in combination. The content of the polymerization accelerator (i) is not particularly limited. In view of, for example, the curability of the resultant self-adhesive dental composite resin, the content of the polymerization accelerator (i) is preferably 0.001 to 30 parts by mass, more preferably 0.01 to 10 parts by mass, and most preferably 0.1 to 5 parts by mass, with respect to 100 parts by mass of the total polymerizable monomers. The content of the polymerization accelerator (i) may be 0.05 parts by mass or more and 20 parts by mass or less with respect to 100 parts by mass of the total polymerizable monomers. When the content of the polymerization accelerator (i) is less than 0.001 parts by mass with respect to 100 parts by mass of the total polymerizable monomers, polymerization may not proceed sufficiently and thus adhesiveness may be reduced. On the other hand, when the content of the polymerization accelerator (i) is more than 30 parts by mass with respect to 100 parts by mass of the total polymerizable monomers, depending on the polymerizability of the polymerization initiator itself, sufficient adhesiveness may not be obtained and, furthermore, the polymerization accelerator (i) may be segregated from the self-adhesive dental composite resin.

The self-adhesive dental composite resin of the present invention may further comprise a fluorine ion-releasing material (j). The addition of the fluorine ion-releasing material (j) to the self-adhesive dental composite resin can provide acid resistance to tooth structures. Examples of the fluorine ion-releasing material include metal fluorides such as sodium fluoride, potassium fluoride, sodium monofluorophosphate, lithium fluoride, and ytterbium fluoride. As fluorine ion-releasing materials (j), one of these may be contained alone, or two or more thereof may be used in combination.

A preferred embodiment of the self-adhesive dental composite resin of the present invention is: a self-adhesive dental composite resin comprising a polymerizable monomer, the photopolymerization initiator (c), and filler (d), wherein the polymerizable monomer includes the acid group-containing (meth)acrylic polymerizable monomer (a), polyfunctional (meth)acrylic polymerizable monomer (b) containing no acid group, and amide proton-containing polyfunctional (meth)acrylamide polymerizable monomer (e); or a self-adhesive dental composite resin containing a polymerizable monomer, the photopolymerization initiator (c), and filler (d), wherein the polymerizable monomer includes the acid group-containing (meth)acrylic polymerizable monomer (a), polyfunctional (meth)acrylic polymerizable monomer (b) containing no acid group, and hydrophilic monofunctional polymerizable monomer (f).

Another preferred embodiment is a self-adhesive dental composite resin comprising a polymerizable monomer, the photopolymerization initiator (c), and filler (d), wherein the polymerizable monomer includes the acid group-containing (meth)acrylic polymerizable monomer (a), polyfunctional (meth)acrylic polymerizable monomer (b) containing no acid group, amide proton-containing polyfunctional (meth)acrylamide polymerizable monomer (e), and hydrophilic monofunctional polymerizable monomer (f).

Yet another preferred embodiment is a self-adhesive dental composite resin comprising a polymerizable monomer, the photopolymerization initiator (c), and filler (d), wherein the polymerizable monomer includes the acid group-containing (meth)acrylic polymerizable monomer (a), polyfunctional (meth)acrylic polymerizable monomer (b) containing no acid group, amide proton-containing polyfunctional (meth)acrylamide polymerizable monomer (e), and hydrophilic monofunctional polymerizable monomer (f), the polyfunctional (meth)acrylic polymerizable monomer (b) containing no acid group includes the difunctional aliphatic polymerizable monomer, the amide proton-containing polyfunctional (meth)acrylamide polymerizable monomer (e) includes the polyfunctional (meth)acrylamide polymerizable monomer (e3) represented by the general formula (5), the hydrophilic monofunctional polymerizable monomer (f) includes the hydrophilic monofunctional (meth)acrylate polymerizable monomer.

An additional preferred embodiment is a self-adhesive dental composite resin comprising a polymerizable monomer, the photopolymerization initiator (c), and filler (d), wherein the polymerizable monomer includes the acid group-containing (meth)acrylic polymerizable monomer (a), polyfunctional (meth)acrylic polymerizable monomer (b) containing no acid group, amide proton-containing polyfunctional (meth)acrylamide polymerizable monomer (e), and hydrophilic monofunctional polymerizable monomer (f), wherein the content of the acid group-containing (meth)acrylic polymerizable monomer (a) is 1 to 40 parts by mass, the content of the polyfunctional (meth)acrylic polymerizable monomer (b) containing no acid group is 30 to 95 parts by mass, the content of the amide proton-containing polyfunctional (meth)acrylamide polymerizable monomer (e) is 0.5 to 30 parts by mass, and the content of the hydrophilic monofunctional polymerizable monomer (f) is 1 to 30 parts by mass in 100 parts by mass of the total polymerizable monomer components.

In any of the above preferred embodiments, appropriate adjustment of the contents of the components, appropriate selection of the types of the compounds, and addition or omission of the optional components (for example, the polymerization accelerator (i), chemical polymerization initiator, and polymerization inhibitor) can be done on the basis of the foregoing description.

Furthermore, for example, a pH adjuster, polymerization inhibitor, ultraviolet absorber, thickener, colorant, antibacterial agent, and flavor may be added to the self-adhesive dental composite resin of the present invention as long as the effect of the present invention is not impaired.

The self-adhesive dental composite resin of the present invention may preferably be a one-part or multi-part self-adhesive dental composite resin. Of these, a one-part type is the more preferred in view of the ease of handling.

The present invention encompasses embodiments obtainable by combining the above features in various manners within the technical scope of the present invention as long as the effect of the present invention can be obtained.

EXAMPLES

Hereinafter, the present invention will be described in detail by way of examples and comparative examples. The present invention is not limited by these examples. Abbreviations used hereinafter are as follows. Except for compounds for which synthesis methods are specifically described, compounds used in the following examples and comparative examples are commercially-available products.

[Acid Group-Containing (Meth)Acrylic Polymerizable Monomer (a)]

MDP: 10-methacryloyloxydecyl dihydrogen phosphate 4-META: 4-[2-(methacryloyloxy)ethoxycarbonyl]phthalic acid anhydride

[Polyfunctional (Meth)Acrylic Polymerizable Monomer (b) Containing No Acid Group]

UDMA: 2,2,4-trimethylhexamethylenebis(2-carbamoyloxyethyl) dimethacrylate Bis-GMA: 2,2-bis[4-(3-methacryloyloxy-2-hydroxypropoxy)phenyl]propane D-2.6E: 2,2-bis(4-methacryloyloxypolyethoxyphenyl)propane (having an average number of moles of added ethoxy groups of 2.6) TEGDMA: Triethylene glycol dimethacrylate

[Photopolymerization Initiator (c)]

CQ: D1-camphorquinone BAPO: Bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide

[Amide Proton-Containing Polyfunctional (Meth)Acrylamide Polymerizable Monomer (e)]

TAC4: N,N′,N″,N′″-tetraacryloyltriethylenetetramine (compound (e1-5) represented by the following formula):

MAEA: N-methacryloyloxyethyl acrylamide (asymmetric polyfunctional (meth)acrylamide polymerizable monomer represented by the following formula):

[Hydrophilic Monofunctional Polymerizable Monomer (f)]

DEAA: N,N-diethylacrylamide

HEMA: 2-hydroxyethyl methacrylate

[Filler (h)]

Surface-treated silica: Silane-treated silica powder Silica powder (manufactured by Nitchitsu Co., Ltd. under the trade name of Hi-Silica) was ground in a ball mill to obtain a pulverized silica powder. The pulverized silica powder thus obtained was measured using a laser diffraction particle size distribution analyzer (model “SALD-2 100” manufactured by Shimadzu Corporation) to obtain the average particle diameter, which was 2.2 μm. By a conventional method, 100 parts by mass of this pulverized silica powder was surface-treated with 4 parts by mass of 3-methacryloyloxypropyltrimethoxysilane. Surface-treated silica was thus obtained.

Surface-Treated Ba Glass Powder: Silane-Treated Ba Glass Powder

Barium glass (product code “E-3000” manufactured by Esstech, Inc.) was ground in a ball mill to obtain a barium glass powder. The barium glass powder thus obtained was measured using a laser diffraction particle size distribution analyzer (model “SALD-2100” manufactured by Shimadzu Corporation) to obtain the average particle diameter, which was 2.4 μm. By a conventional method, 100 parts by mass of this barium glass powder was surface-treated with 3 parts by mass of 3-methacryloyloxypropyltrimethoxysilane. A surface-treated Ba glass powder was thus obtained.

SiO₂-Coated YBF: Silica-Coated Ytterbium Fluoride

A commercially-available product (SG-YBF 100WSCMP 10; average particle diameter: 110 nm; spherical shape; manufacturer: Sukgyung AT Co., Ltd.) was used as it is.

Spherical Nanosilica: Silane-Treated Colloidal Silica Powder

A commercially-available product (Sciqas (treated with methacrylsilane); average particle diameter: 50 nm; manufacturer: SAKAI CHEMICAL INDUSTRY CO., LTD.) was used as it is.

Fumed Silica: Silan-Treated Colloidal Silica Powder

To 100 parts by mass of distilled water were added 0.3 parts by mass of acetic acid and 3 parts by mass of 3-methacryloyloxypropyltrimethoxysilane, and the resultant mixture was stirred. An amount of 50 parts by mass of a colloidal silica powder (manufactured by Nippon Aerosil Co., Ltd. under the trade name of AEROSIL OX 50 and having an average particle diameter of about 40 nm) was further added, and the resultant mixture was stirred for 1 hour. Water was removed by freeze-drying, followed by heat treatment at 80° C. for 5 hours to obtain a silane-treated colloidal silica powder.

[Polymerization Accelerator (i)]

DABE: Ethyl 4-(N,N-dimethylamino)benzoate

[Others]

BHT: 2,6-di-t-butyl-4-methylphenol (stabilizer (polymerization inhibitor))

Production Example 1

Production of Filler (d-1)

As silica particles, SNOWTEX OL (manufactured by Nissan Chemical Industries, Ltd., having an average particle diameter of 50 nm, dispersed in water, and having a solid content concentration of 20%), which is a type of colloidal silica, was provided. As alcohol, isopropanol was provided. As the silane coupling agent (A), 3-methacryloyloxypropyltrimethoxysilane (KBM-503 manufactured by Shin-Etsu Chemical Co., Ltd.) was provided. As the organosilazane (B), 1,1,1,3,3,3-hexamethyldisilazane (HMDS, HDMS-1 manufactured by Shin-Etsu Chemical Co., Ltd.) was provided. An amount of 60 parts by mass of isopropanol was added to 100 parts by mass of a slurry containing the silica particles dispersed at a concentration of 20 mass % in water. The resultant mixture was mixed at room temperature (about 25° C.) to obtain a dispersion containing the silica particles dispersed in a liquid medium. To the dispersion were added 0.48 parts by mass of 3-methacryloyloxypropyltrimethoxysilane and 0.01 parts by mass of a polymerization inhibitor (3,5-dibutyl-4-hydroxytoluene (BHT) manufactured by KANTO CHEMICAL CO., INC.), and the resultant mixture was mixed at 40° C. for 72 hours. A hydroxy group existing on the surface of the silica particles was surface-treated with the silane coupling agent (A) in this step. Here, 3-methacryloyloxypropyltrimethoxysilane was added so that the surface of a necessary amount (a portion) of the hydroxy group would remain untreated. Next, 0.78 parts by mass of 1,1,1,3,3,3-hexamethyldisilazane was added to the mixture, and the resultant mixture was left at 40° C. for 72 hours. The silica particles were surface-treated in this step, and thus a silica particle material was obtained. Along with the progress of the surface treatment, the silica particles became hydrophobic and unable to stably exist in water and isopropanol, and therefore underwent aggregation and precipitation. In the surface treatment agent, the molar ratio between 3-methacryloyloxypropyltrimethoxysilane and hexamethyldisilazane was 2:5. To the total amount of the mixture obtained after the surface treatment was added 2.6 parts by mass of a 35% aqueous solution of hydrochloric acid to precipitate the silica particle material. The precipitate was collected by filtration using a filter paper (5A manufactured by Advantec Toyo Kaisha, Ltd.). The filtration residue (solids) was washed with pure water and then vacuum-dried at 100° C. to obtain a filler (d-1).

Production Example 2

Production of Filler (d-2)

A filler (d-2) was produced in exactly the same manner as the method for synthesizing the filler (d-1), except that the content of 1,1,1,3,3,3-hexamethyldisilazane was 2.8 parts by mass. In the surface treatment agent, the molar ratio between 3-methacryloyloxypropyltrimethoxysilane and hexamethyldisilazane was 2:18.

Production Example 3 Synthesis of TAC4

In a 1-liter four-necked flask were put 21.9 g (0.15 mol) of triethylenetetramine (manufactured by Tokyo Chemical Industry Co., Ltd.), 75.9 g (0.75 mol) of triethylamine, 3.7 mg (0.03 mmol) of p-methoxyphenol, and 250 mL of dichloromethane, which were stirred and cooled to an internal temperature of 2° C. An amount of 100 mL of a dichloromethane solution of acrylic acid chloride (67.9 g, 0.75 mol) was added dropwise at 5° C. or lower over 2 hours. After the dropwise addition of the solution, the resultant mixture was stirred for 24 hours under the conditions of room temperature. The resultant reaction solution was filtered, and insoluble matters were washed with dichloromethane, and concentration was performed at 35° C. or lower under reduced pressure. The concentrated residue thus obtained was purified by silica gel column chromatography (developing solvent having a ratio of ethyl acetate:methanol=4:1). After the column purification, the solvent was removed under reduced pressure using a rotary evaporator to obtain a white solid. The solid was subjected to LC-MS analysis and ¹H-NMR measurement. It was determined from the locations and integrals of signals that the white solid obtained was a target compound. The weight yield was 12.7 g, and the percentage yield was 23.3%.

MS m/z: 363 (M+H)⁺

¹H-NMR (270 MHz D₂O): δ3.37 (m, 6H), 3.57 (m, 6H), 5.66 (m, 4H), 6.07 (m, 6H), 6.56 (m, 2H) (ppm)

Production Example 4 Synthesis of MAEA

In a 10-liter four-necked flask were put 172.7 g (1.5 mol) of hydroxyethyl acrylamide (manufactured by Kohjin Film & Chemicals Co., Ltd.), 167 g (1.65 mol) of triethylamine, 38 mg (0.3 mmol) of p-methoxyphenol, and 1500 mL of anhydrous tetrahydrofuran, which were stirred and cooled to an internal temperature of −10° C. An amount of 700 mL of an anhydrous tetrahydrofuran solution of methacrylic acid chloride (172.5 g, 1.65 mol) was added dropwise at 5° C. or lower over 2 hours. After the dropwise addition of the solution, the resultant mixture was stirred for 24 hours under the conditions of room temperature. The resultant reaction solution was filtered, and insoluble matters were washed with ethyl acetate. The filtrate was concentrated under reduced pressure, and the residue was dissolved in ethyl acetate. The resultant solution was filtered with Celite to remove a small amount of insoluble matters, and then the filtrate was washed with a mixture of saturated saline solution and purified water (1:1). The organic layer was dried with anhydrous sodium sulfate, and concentration was performed at 35° C. or lower under reduced pressure. The concentrated residue thus obtained was purified by silica gel column chromatography (developing solvent: ethyl acetate). After the column purification, the solvent was removed under reduced pressure using a rotary evaporator to obtain a pale yellow liquid. The liquid was subjected to LC-MS analysis and ¹H-NMR measurement. It was determined from the locations and integrals of signals that the pale yellow liquid thus obtained was a target compound. The weight yield was 201.2 g, and the percentage yield was 73.3%.

MS m/z: 184 (M+H)⁺

¹H-NMR (270 MHz CDCl₃): δ1.94 (m, 3H), 3.62 (m, 2H), 4.28 (m, 2H), 5.58 (m, 1H), 5.66 (m, 1H), 6.08 (s, 1H), 6.10 (m, 1H), 6.11 (m, 1H), 6.28 (m, 1H) (ppm)

Examples 1 to 14 and Comparative Examples 1 to 6

Using the materials, for example, those prepared in the above production examples, self-adhesive dental composite resins of Examples 1 to 14 and dental composite resins of Comparative Examples 1 to 6 were each prepared by mixing all the components, other than the filler (d) or (h) (powder), specified in Table 1, 2, or 3 at ordinary temperature to obtain a homogeneous liquid component and mixing the homogeneous liquid component thus obtained and filler (d) or (h) (powder). Next, the consistency, transparency of a paste, tensile bond strength to dentin, and flexural strength were measured using these dental composite resins by the following methods. Tables 1 to 3 show the contents (parts by mass) of the components of these dental composite resins and the test results thereof.

[Consistency]

After defoamed under vacuum, each of the prepared dental composite resins of Examples and Comparative Examples was loaded into a syringe (a container for Clearfil Majesty LV; inner diameter: 8 mm; length: 63 mm) made of a polyolefin resin and allowed to stand at 25° C. for 2 hours. A sample for the consistency test was thus prepared. An amount of 0.5 mL of the sample was weighed out, and allowed to stand on the center of a glass sheet (5 cm×5 cm) in the shape of a mound in a thermostatic chamber set at 25° C. (humidity: 40%). A 40 g glass sheet (5 cm×5 cm) was placed on the sample, and after 120 seconds, the longest diameter and shortest diameter of the sample were measured over the glass sheet. The arithmetic average of the two diameters was calculated and employed as the consistency (mm). The longest diameter of the sample refers to the longest one of the diameters that pass through the center of the sample, and the shortest diameter of the sample refers to one of the diameters that pass through the center of the sample, the one orthogonal to the longest diameter of the sample. After defoamed under vacuum, loaded into a syringe made of a polyolefin resin, and allowed to stand in a thermostat set at 60° C. for 4 weeks, each of the dental composite resins was measured in the above-described manner. The resultant value was employed as the consistency measured after the 4-week storage at 60° C.

[Transparency of Dental Composite Resin]

A stainless steel mold having a diameter of 20 mm and a thickness of 1 mm was set on a glass slide. Into the mold was loaded each of the dental composite resins to slightly overflow. A glass slide was placed over the top, and power was applied from above to push an excess of the composite resin out of the mold. A sample for evaluating the transparency of the dental composite resin was thus obtained.

A lightness (L1) representing a lightness index L* in the L*a*b* color system defined in JIS Z 8781-4: 2013 for the case where a standard white plate was set behind the sample and a lightness (L2) representing a lightness index L* in the L*a*b* color system for the case where a standard black plate was set behind the same sample were measured using a spectrocolorimeter (CM-3610d meeting the condition c defined in JIS Z 8722: 2009 and manufactured by KONICA MINOLTA JAPAN, INC.). The difference between the two values of lightness (ΔL=L1−L2) was calculated and employed as a measure of the degree of transparency. A larger value of ΔL indicates higher transparency. A large value of ΔL is considered suitable. ΔL is preferably 15.0 or more and more preferably 18.0 or more. After defoamed under vacuum, loaded into a syringe made of a polyolefin resin, and allowed to stand in a thermostat set at 60° C. for 4 weeks, each of the dental composite resins was measured in the above-described manner. The measured value was employed as the transparency of the dental composite resin measured after the 4-week storage at 60° C.

[Tensile Bond Strength to Dentin]

The labial surfaces of bovine mandibular incisors were each ground with #80 silicon carbide paper (manufactured by Nihon Kenshi Co., Ltd.) under running water to obtain samples with an exposed flat dentin surface. Each of the obtained samples was further ground with #1000 silicon carbide paper (manufactured by Nihon Kenshi Co., Ltd.) under running water. After the completion of grinding, the sample was dried by blowing air over water on the surface. To the dried smooth surface was attached an about 150-μm-thick adhesive tape having a circular hole of 3 mm diameter, so that an adhesive area was defined.

Each of the prepared dental composite resins of Examples and Comparative Examples was applied within the circular hole, which was covered with a release film (made of polyester). Next, a glass slide was placed on and pressed against the release film to flatten the surface of the applied dental composite resin. Subsequently, the applied dental composite resin was cured by 10-second light irradiation through the release film using a dental visible light irradiation device (manufactured by Morita Corporation under the trade name “PenCure 2000”) for polymerization to obtain a cured product.

Next, a cylindrical stainless steel rod (having a diameter of 7 mm and a length of 2.5 cm) was bonded at its one end face (circular end face) to the surface of the obtained cured product of the dental composite resin using a commercially-available dental resin cement (manufactured by Kuraray Noritake Dental Inc. under the trade name “PANAVIA (registered trademark) 21”) to obtain a sample. The sample was allowed to stand at room temperature for 30 minutes, and then immersed in distilled water. There were fabricated 5 such bond test samples, and these samples were allowed to stand in a thermostat set at 37° C. for 24 hours.

The bond test samples were measured for the tensile bond strength using a universal testing machine (manufactured by Shimadzu Corporation) with a crosshead speed set at 2 mm/minute. The average of the measured values was employed as the value of the tensile bond strength.

[Flexural Strength]

Each of the prepared dental composite resins of Examples and Comparative Examples was defoamed under vacuum and loaded into a stainless steel mold (having dimensions of 2 mm×2 mm×25 mm). Glass slides were pressed against the upper and lower surfaces of the dental composite resin, and each of the two surfaces was subjected to light irradiation at 5 points for 10 seconds per point using a dental visible light irradiation device (manufactured by Morita Corporation under the trade name “PenCure 2000”) for polymerization. The dental composite resin was thus cured to obtain a cured product. For each of Examples and Comparative Examples, 5 such cured products were fabricated as samples. Each of the cured products was taken out of the mold and then stored in 37° C. distilled water for 24 hours. The flexural strength of each sample was measured using a precision universal testing machine (manufactured by Shimadzu Corporation under the trade name of “AGI-100”) under conditions where the span between supports was 20 mm and the crosshead speed was 1 mm/minute. The average of the measured values of the samples was calculated and employed as the value of the flexural strength.

TABLE 1 Exam- Exam- Exam- Exam- Exam- Exam- Exam- Exam- Component (parts by mass) ple 1 ple 2 ple 3 ple 4 ple 5 ple 6 ple 7 ple 8 Acid group-containing (meth)acrylic MDP 10 10 10 10 10 10 10 10 polymerizable monomer (a) 4-META Polyfunctional (meth)acrylic UDMA 61 59 62 60 61 61 polymerizable monomer (b) Bis-GMA 41 containing no acid group D-2.6E 41 TEGDMA 10 30 30 10 10 10 10 10 Amide proton-containing MAEA 10 10 10 10 3 5 10 10 polyfunctional (meth)acrylamide TAC4 2 polymerizable monomer (e) Hydrophilic monofunctional DEAA 9 polymerizable monomer (f) HEMA 9 9 9 9 15 15 9 Photopolymerization initiator (c) CQ 0.2 0.2 0.2 0.2 0.2 0.2 0.2 0.2 BAPO Polymerization accelerator (i) DABE 0.4 0.4 0.4 0.4 0.4 0.4 0.4 0.4 Polymerization inhibitor BHT 0.1 0.1 0.1 0.1 0.1 0.1 0.1 Filler (d) Filler (d-1) 180 180 180 180 180 180 180 Filler (d-2) 180 Filler (h) Surface-treated silica Surface-treated Ba glass powder SiO₂-coated YBF Spherical nanosilica Fumed silica Consistency measured just after preparation (mm) 23.0 20.0 21.0 23.1 23.5 23.3 20.1 21.5 Consistency measured after 4-week storage 23.1 19.9 20.5 22.8 23.3 23.0 19.9 21.2 at 60° C. (mm) Difference between consistency measured just −0.1 0.1 0.5 0.3 0.2 0.3 0.2 0.3 after preparation and consistency measured after 4-week storage at 60° C. (mm) Transparency of paste measured just after 26.0 22.1 20.1 25.6 27.5 26.5 24.2 25.1 preparation (ΔL) Transparency of paste measured after 4-week 25.3 20.7 18.9 25.1 26.8 25.9 24.0 24.7 storage at 60° C. (ΔL) Difference between transparency measured just 0.7 1.4 1.2 0.5 0.7 0.6 0.2 0.4 after preparation and transparency measured after 4-week storage at 60° C. (ΔL) Tensile bond strength to dentin (MPa) 12.8 12.8 12.8 12.8 12.8 12.8 12.8 12.8 Flexural strength (MPa) 108.2 120.1 119.4 100.1 98.8 103.4 105.2 104.5

TABLE 2 Exam- Exam- Exam- Exam- Exam- Exam- Component (parts by mass) ple 9 ple 10 ple 11 ple 12 ple 13 ple 14 Acid group-containing (meth)acrylic MDP 10 3 25 10 10 polymerizable monomer (a) 4-META 10 Polyfunctional (meth)acrylic UDMA 61 61 68 51 61 61 polymerizable monomer (b) Bis-GMA containing no acid group D-2.6E TEGDMA 10 10 10 10 10 10 Amide proton-containing MAEA 10 10 10 10 10 10 polyfunctional (meth)acrylamide TAC4 polymerizable monomer (e) Hydrophilic monofunctional DEAA polymerizable monomer (f) HEMA 9 9 9 9 9 9 Photopolymerization CQ 0.2 0.2 0.2 0.2 0.2 initiator (c) BAPO 1 Polymerization accelerator (i) DABE 0.4 0.4 0.4 0.4 0.4 Polymerization inhibitor BHT 0.1 0.1 0.1 0.1 0.1 0.1 Filler (d) Filler (d-1) 180 180 180 180 255 125 Filler (d-2) Filler (h) Surface-treated silica Surface-treated Ba glass powder SiO₂-coated YBF Spherical nanosilica Fumed silica Consistency measured just after preparation (mm) 23.0 22.8 22.7 23.0 18.2 24.1 Consistency measured after 4-week storage at 22.8 22.6 22.4 22.8 17.9 23.8 60° C. (mm) Difference between consistency measured just 0.2 0.2 0.3 0.2 0.3 0.3 after preparation and consistency measured after 4-week storage at 60° C. (mm) Transparency of paste measured just after 25.6 24.5 26.6 26.4 27.2 26.2 preparation (ΔL) Transparency of paste measured after 4-week 24.8 24.0 25.7 26.1 26.9 25.4 storage at 60° C. (ΔL) Difference between transparency measured 0.8 0.5 0.9 0.3 0.3 0.8 just after preparation and transparency measured after 4-week storage at 60° C. (ΔL) Tensile bond strength to dentin (MPa) 12.8 12.8 12.8 12.8 12.8 12.8 Flexural strength (MPa) 100.2 103.9 108.9 96.7 128.9 98.7

TABLE 3 Comparative Comparative Comparative Comparative Comparative Comparative Component (parts by mass) Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Acid group-containing (meth)acrylic MDP 10 10 10 10 10 10 polymerizable monomer (a) 4-META Polyfunctional (meth)acrylic UDMA 61 61 polymerizable monomer (b) Bis-GMA 41 containing no acid group D-2.6E 41 41 41 TEGDMA 10 10 30 30 30 30 Amide proton-containing AIAEA 10 10 10 10 10 10 polyfunctional (meth)acrylamide TAC4 polymerizable monomer (e) Hydrophilic monofunctional DEAA polymerizable monomer (f) HEMA 9 9 9 9 9 9 Photopolymerization CQ 0.2 0.2 0.2 0.2 0.2 0.2 initiator (c) BAPO Polymerization accelerator (i) DABE 0.4 0.4 0.4 0.4 0.4 0.4 Polymerization inhibitor BHT 0.1 0.1 0.1 0.1 0.1 0.1 Filler (d) Filler (d-1) Filler (d-2) Filler (h) Surface-treated 300 350 125 200 silica Surface-treated 300 Ba glass powder SiO₂-coated YBF 42 Spherical nanosilica 180 Fumed silica 15 15 15 15 Consistency measured just after preparation (mm) 24.1 40.1 35.1 49.4 39.8 39.8 Consistency measured after 4-week storage at Solidified* Solidified* Solidified* Solidified* 5.1 Solidified* 60° C. (mm) Difference between consistency measured just — — — — 34.7 — after preparation and consistency measured after 4-week storage at 60° C. (mm) Transparency of paste measured just after 25.4 13.1 12.1 11.9 13.0 9.9 preparation (ΔL) Transparency of paste measured after 4-week — — — — 1.1 — storage at 60° C. (ΔL) Difference between transparency measured just — — — — 11.9 — after preparation and transparency measured after 4-week storage at 60° C. (ΔL) Tensile bond strength to dentin (MPa) 11.2 10.2 11.3 7.9 9.9 10.4 Flexural strength (MPa) 99.0 128.3 142.1 141.7 139.1 105.6 *Because the paste turned hard, the measurement was unable to be performed.

As shown in Tables 1 and 2, the self-adhesive dental composite resins (Examples 1 to 14) according to the present invention show little change in consistency; that is, the difference between the consistency measured just after the preparation and the consistency measured after the 4-week storage at 60° C. is 1 mm or less. Moreover, little change is observed in the difference between the transparency measured just after the preparation and the transparency measured after the 4-week storage at 60° C.; that is, ΔL is 2 or less. Furthermore, each of the self-adhesive dental composite resins exhibits a tensile bond strength to dentin of 10 MPa or more and a flexural strength of 90 MPa or more.

As shown in Table 3, the dental composite resins of Comparative Examples 1, 2, 3, 4, and 6 containing no filler (d) of the present invention and employing the silica particles surface-treated with the silane coupling agent (A) alone were solidified after the 4-week storage at 60° C.

The dental composite resin of Comparative Example 5 containing no filler (d) of the present invention and employing the barium glass powder surface-treated with the silane coupling agent (A) alone underwent a significant change in consistency and transparency after the 4-week storage at 60° C.

INDUSTRIAL APPLICABILITY

The self-adhesive dental composite resin of the present invention can be used for treatment of a broken or chipped tooth or dental caries by first forming a cavity in the tooth and then injecting the self-adhesive dental composite resin directly into the cavity and photocuring the self-adhesive dental composite resin. 

1: A self-adhesive dental composite resin, comprising: an acid group-containing (meth)acrylic polymerizable monomer (a); a polyfunctional (meth)acrylic polymerizable monomer (b) containing no acid group; a photopolymerization initiator (c); and a filler (d), wherein the filler (d) is treated with a surface treatment agent and has an average particle diameter of 0.01 to 50.0 μm, the surface treatment agent comprises a silane coupling agent (A) of formula (1): CH₂═C(R¹)—COO—(CH₂)_(p)—Si—R² _(q)R³ _((3-q))  (1), wherein R¹ is a hydrogen atom or a methyl group, R² is an optionally substituted hydrolyzable group, R³ is an optionally substituted C₁ to C₃ alkyl group, p is an integer of 1 to 13, and q is 2 or 3, and an organosilazane (B) of formula (2): R⁴R⁵R⁶—Si—NH—Si—R⁷R⁸R⁹  (2), wherein R⁴, R⁵, and R⁶ are each independently a hydrogen atom or an optionally substituted C₁ to C₃ alkyl group, at least one of R⁴, R⁵, and R⁶ is an optionally substituted C₁ to C₃ alkyl group, R⁷, R⁸, and R⁹ are each independently a hydrogen atom or an optionally substituted C₁ to C₃ alkyl group, and at least one of R⁷, R⁸, and R⁹ is an optionally substituted C₁ to C₃ alkyl group. 2: The self-adhesive dental composite resin according to claim 1, wherein R² is an unsubstituted hydrolyzable group, R³ is an unsubstituted C₁ to C₃ alkyl group, R⁴, R⁵, and R⁶ are each independently a hydrogen atom or an unsubstituted C₁ to C₃ alkyl group, at least one of R⁴, R⁵, and R⁶ is an unsubstituted C₁ to C₃ alkyl group, R⁷, R⁸, and R⁹ are each independently a hydrogen atom or an unsubstituted C₁ to C₃ alkyl group, and at least one of R⁷, R⁸, and R⁹ is an unsubstituted C₁ to C₃ alkyl group. 3: The self-adhesive dental composite resin according to claim 1, wherein R² is an unsubstituted linear or branched C₁ to C₆ alkoxy group. 4: The self-adhesive dental composite resin according to claim 1, wherein R¹ is a methyl group. 5: The self-adhesive dental composite resin according to claim 1, wherein p is 2 to
 10. 6: The self-adhesive dental composite resin according to claim 1, wherein q is
 3. 7: The self-adhesive dental composite resin according to claim 1, wherein the silane coupling agent (A) is at least one selected from the group consisting of 2-methacryloyloxyethyltrimethoxysilane, 3-methacryloyloxypropyltrimethoxysilane, 4-methacryloyloxybutyltrimethoxysilane, 5-methacryloyloxypentyltrimethoxysilane, and 6-methacryloyloxyhexyltrimethoxysilane. 8: The self-adhesive dental composite resin according to claim 1, wherein the organosilazane (B) is at least one selected from the group consisting of 1,1,3,3-tetramethyldisilazane, 1,1,1,3,3,3-hexamethyldisilazane, and 1,1,1,3,3-pentamethyldisilazane. 9: The self-adhesive dental composite resin according to claim 1, wherein a molar ratio between the silane coupling agent (A) and the organosilazane (B) is [silane coupling agent (A)]:[organosilazane (B)]=1:1 to 1:20. 10: The self-adhesive dental composite resin according to claim 1, wherein a content of the acid group-containing (meth)acrylic polymerizable monomer (a) is 1 to 40 parts by mass and a content of the polyfunctional (meth)acrylic polymerizable monomer (b) containing no acid group is 30 to 95 parts by mass in 100 parts by mass of the total polymerizable monomer components, and a content of the photopolymerization initiator (c) is 0.001 to 20 parts by mass and a content of the filler (d) is 1 to 80 parts by mass with respect to 100 parts by mass of the total polymerizable monomer components. 11: The self-adhesive dental composite resin according to claim 1, further comprising an amide proton-containing polyfunctional (meth)acrylamide polymerizable monomer (e). 12: The self-adhesive dental composite resin according to claim 11, wherein a content of the amide proton-containing polyfunctional (meth)acrylamide polymerizable monomer (e) is 0.5 to 30 parts by mass in 100 parts by mass of the total polymerizable monomer components. 13: The self-adhesive dental composite resin according to claim 1, further comprising a hydrophilic monofunctional polymerizable monomer (f). 14: The self-adhesive dental composite resin according to claim 13, wherein the hydrophilic monofunctional polymerizable monomer (f) is at least one selected from the group consisting of a hydrophilic monofunctional (meth)acrylate polymerizable monomer and a hydrophilic monofunctional (meth)acrylamide polymerizable monomer. 15: The self-adhesive dental composite resin according to claim 13, wherein a content of the hydrophilic monofunctional polymerizable monomer (f) is 1 to 30 parts by mass in 100 parts by mass of the total polymerizable monomer components. 16: The self-adhesive dental composite resin according to claim 1, being a one-part self-adhesive dental composite resin. 